Reasons to use an aspect ratio of 2:1

Apparently 2.00:1 is called "Univisium".

16:9 (1.77:1) is common for TV shows but films tend to have wider aspects - 1.85:1 or 2.35:1. Because they're used for films, they have a "cinematic" feeling. The implication with this 2:1 size is that it will be a compromise that all films and TV shows can use so that we don't have dozens of different aspect ratios.

From the above linked Wikipedia page:

In 1998, cinematographer Vittorio Storaro announced his plans for a new film format, originally to be called Univision, in an interview with International Photographer magazine, As Storaro stated in his written proposal "Recently, any movie - no matter how big or small, successful or not - will, after a very short life on the big screen, have a much longer life on an electronic screen. Today the Answer Print is made for both of these two different media. ...Having these two different media, with essentially two different aspect ratios, each of us (Directors, Production Designers, Cinematographers, Camera Operators, etc.) shares the nightmare of compromising the Composition of the Image. Looking through a viewfinder, a camera, or a monitor, we are always faced with at least two images of the same subject."

Storaro opines that, in the future of cinema, all films will be photographed in either high-definition video for small, intimate digital projection theaters, or in 65 mm for "big audience... large screen" films. In the cinematographer's opinion, as all films will be one of the two formats, he suggests a common aspect ratio compromise of 2.00:1 (mathematical average of 65 mm 2.20:1 and HD 1.78:1) be adopted for all films, 65 mm theatrical, HD theatrical and television.

There are actually some technical benefits to this aspect ratio but they generally apply to film only and with the move towards digital recording and presentation, while by no means total (if ever likely to be), these benefits are questionable... particularly considering that the shows you mention were shot digitally, generally on the RED.

It's worth noting that the creator of this concept also prescribes shooting in 25 fps (rather than the standard 24), which simplifies conversion to PAL and SECAM without making NTSC conversion significantly more complicated.

In general, while he has made films using this aspect ratio, outside the shows you mention and A Series of Unfortunate Events, few major productions have used this aspect ratio.

If you'd like to read what Storaro himself said about this in full, his article (in PDF format) can be found here.

Perhaps, the producers of these TV shows just wanted to go away from the HDTV look. So did the producers of "Jurassic World", when opting for an aspect ratio of 2:1:

Schwartzman, an anamorphic advocate, wanted to shoot the film in 2.40:1, but executive producer Steven Spielberg preferred 1.85:1 because that ratio provided enough headroom for the dinosaurs. “Director Colin Trevorrow and I felt like 1:85 was too much like high-definition television in terms of an aspect ratio,” the cinematographer says. “That's where we conceived a 2.00:1 aspect ratio. We made a ground glass and shot some tests. It was such a great way to frame. It has the benefits of 2.40 without losing all the headroom.

Source

At the same time, the Red Digital Cinema Camera Company has made the 2:1 ratio popular, because the RED cameras offer a lot of modes to shoot in that ratio, as seen in this manual page, which shows the formats available on the RED EPIC DRAGON. Since "House of Cards" and "Stranger Things" are shot on the RED, maybe this seemed like a good and easy way to go.

"Transparent" has been shot with the Canon EOS C500. It does not offer a native 2:1 mode, but a recording resolution of 4096 x 2160 (DCI 4K resolution), which has an aspect ratio of approx. 1.9:1. They must have cropped the image in the post-production process.

I have been a fan of 2:1 aspect for a long time and even "pitched" this years ago online. For me, it would make things much easier to process on computers because of the perfect ratio (2:1) instead of some oddball 16:9. Things like video algorithms, (especially recursive algorithms), would not have to handle the "extra slivers" of video information in the 16:9 format vs. 16:8 so it would make them simpler. This 16:9 crap in my opinion is just that, crap. Since it is used mostly in computer monitors and computers "love" powers of 2, it should have been an easy choice to use 16:8 (2:1) instead.