Are more movie stars acting in TV shows nowadays (and if so, why)?

TV has become, in the opinion of many Directors/Actors, the most creatively fertile ground.

In the last few years we have seen an exodus of talent from Hollywood, and those who have left have been so provoked by the current climate of film making they have felt the need to not only abandon the Hollywood system, but make public declarations as to their reasons.

We've lost the two greatest 'Stevens' (Spielberg and Soderbergh) in the last few years, both of whom have blamed the monopolization of Studio based mainstream content and escalating budgets. From Soderbergh, this frustration is understandable: but from Spielberg, who all but invented the concept of a summer blockbuster with Jaws (and is held responsible by many for the death of the New Hollywood, the US film industries most critically successful period) this is an extreme statement indeed: something is amiss in Hollywood, and all the warning lights are flashing vehemently at the minute.

The last time an event as dramatic as the current exodus from Hollywood occurred led to something called the Paramount Decision, which fundamentally and irrevocably altered the landscape of global cinema.

It was decided that certain interests were able to exploit their control over the Hollywood system to monopolize the industry, creating a relative stranglehold on any content not produced by The Big 5. This has repeated itself a number of times since, and different solutions were found...

• In the late 1960's, as a studio monopoly took hold, a movement of opposition called The New Hollywood or Post-Classical Hollywood occurred: producing perhaps the most celebrated directors and actors of all time...

  After this period of rebellion, Spielberg and Lucas began co-operating with the studios again and worked to initiate what became the blockbuster model of movies: they, amongst others, are quite reviled amongst film aesthetes for this betrayal; but in reality, the New Hollywooders were largely out of control in their self-indulgent pursuit of auterism by the time the Blockbusters arrived.

• By the early 1990s, despite the fact that Blockbusters were 'booming', the lack of cinematic opposition within the US system led to the rise of 'the independents' to produce alternative content. Miramax were a fundamental part of this, which again led to a period of creative affluence which produced the likes of Soderberg and Tarrantino.
• In the late noughties, studios had become dependent on a system that used a summer blockbuster to provide the majority of their yearly income. With these pictures competing directly against each other in a release window of only a couple of weeks, budgets inevitably swelled in competition. In the 'Michael Bay' era of cinema, the size of a Movie's Budget is often its own marketing campaign. As a result of this, sincere creative talent has found solace in a medium that is still cinematic, but grants a broader lease of play for its actors/directors/producers. That medium is Television, and as such the Greed of the Studios has unexpectedly created a golden age of Television: long may it reign.

The reason why this last, and current, era is so potently worrying for the industry is because it is the first time since the paramount decision that talent has moved out the industry and into another medium: Television.

In addition, I have to categorically and wholly disagree with CGCambell's assertion that the reason movies stars are getting involved with TV work is because of the 'Paycheck, paycheck, paycheck.'

If you watch most of these shows, you'll quickly realize that in many cases the lead actors are also producers and executive producers: meaning they have sunk personal resources into the projects to make them successful.

There is a reason that the majority of these actors are credible, respected stars who have traditionally pursued diverse roles: they are, on the whole, individuals who have traditionally engaged in the stagecraft of the industry, as opposed to merely phoning it in and picking up the cheque (although this is to be judged on a case by case basis, as opposed to a rule).

There is a reason, for example, that during Matthew McConaughey's cinematic rehabilitation he has contributed directly to the production of the finest TV show of the last 20 years: True Detective... this is not a subjective statement! ;-)

First of all, I have to say that the following is largely based on my own observations and deductions in contrast to elaborate research, and to be seen in addition, if not intertwined, with the reasons presented in the other ansers.

I think a big factor is also the question of availability and distribution. As far as I can see, it wasn't until the advent of DVDs (which I would broadly classify as the beginning of this century) that entire TV-shows became available on home media. This marked the first time that TV-shows actually rose beyond their media and, even more so, beyond their pre-scheduled airing times. And this was even furthered by the rise of internet services like Netflix or Amazon Prime and the like, which make TV shows practically available on demand (imagine the only way to watch your favourite movies was by catching them when they air on TV). This IMHO opened a whole new level of appreciating TV shows apart from mere weekly strictly scheduled entertainment. So the market for distributing TV shows opened to a much larger area in addition to their traditional medium and thus TV shows have became more significant financially.

In addition to the mere financial implications of a bigger and more diverse market this also brought a higher cultural signifance and new ways of consumption. Nowadays it is not uncommon for a TV show to be consumed by Binge Watching by a large amount of viewers. And this I think might be a large contributor to how the stories are told. It has been a long-term observation by me that the amount of continuous serial stories with a large cross-episode development of the characters and story have become more and more prevalent over the last years, a development also adressed in this related question. This might be motivated (or at least largely facilitated) by people watching them in a more continuous or packed fashion. In fact House of Cards, one of the (if not the) first "TV" shows produced explicitly by and for an internet streaming service (and starring the great and movie-famous Kevin Spacey), was published a whole season at once, explicitly facilitating binge-watching. And in fact this in turn has even influenced the classic TV medium, as for example the German TV channel airing Game of Thrones and The Walking Dead shows whole seasons of those in binge-friendly 3-6 epidose blocks on consecutive days.

And I think this trend to more high-quality serialized dramas might also be a reason why the overall story and character development might have become more important, requiring strong, known and charismatic actors to anchor those stories around, and on the other hand providing more interesting "playgrounds" for those actors to express themselves in contrast to your usual "murder of the week" episodes. And it fits the bill that one of the first shows of the modern age of TV to provide an entirely serial plot (where you couldn't miss a single episode) was to my knowdlegde also one of the first to famously feature a former movie actor (even if that actor's movie carrier was already on a rather descending path by then), 24.

In addition to that you nowadays also have many TV shows which are, even if being rather episodic genre shows, explicitly anchored around a unique and remarkable protagonist, for which you on the one hand want both famous and good actors to play those characters and which on the other hand also give those actors an interesting role to excel in, be it for giving those roles the needed gravitas and acting proficiency or for the marketing effect of dragging the viewers to the show. Examples for this are House (Hugh Laurie), Shark (James Woods) or Lie to Me (Tim Roth).

All in all it probably comes down to the medium of TV shows experiencing a general rise in cultural significance and quality (maybe to a large degree due to the factor JohnSmithOptional mentioned in his answer) which in turn makes it more attractive to personnel coming primarily from the "bigger brother" of movies and which then in turn contribute to the quality of the TV shows (kind of a vicious, or rather heavenly, circle) and to the more fleixible ways of distributing your products, be this in a financial or narrative way.