Why did they scrap the old park in Jurassic World?

I had the impression that the management team of the company running Jurassic World is different from the one that was managing Jurassic Park, although some members might be related if I recall correctly members from the first episode even appear, only to be shown leaving the company in reaction to the way it is currently managed.

Now my answer will not be a rational explanation, but one based on behaviors I have seen in real life.

Sometimes when a new team arrives to do a job that was judged to have been done poorly by the previous team; it decides to dump all the work that had previously been done and to start from scratch again, even though some of the work of the old team could be salvaged.

This is of course counter-productive in the long term, but some people might behave like this for various reasons: pressure from higher management to which they respond by trying to pretend they are more "in charge" than the previous team (and berating that old team's achievements helps toward this goal); lack of experience; overconfidence; ego...

According to this point of view, it is easy to see that the new team thinks it can do better than the old one, and does not want to re-use any of the previous attractions.

Another reason could be that this new management team does not want the public to remember what happened to the previous Park (people died horribly!), which would be bad for their business. They want to erase these events from public memory.

This attitude is adressed in the film too, in the scene where we're first introduced to the control center crew and one of them wears a T-shirt with the old Jurassic Park logo, much to Claire's dismay:

Claire: Where did you get that?
Lowery: This? I got it on eBay...
Claire: Didn't occur to you maybe that's in poor taste?
Lowery: The shirt? Yeah, no, it did. I understand people died. It was terrible, but that first park was legit.
Claire: Okay, please don't wear it again.

If you thing this is exaggerated, let me remind you of the example of real life company WWE that removed all occurrences of the name of their former wrestler Chris Benoit from the content they offer, after it was found he was involved in a family murder and suicide case...

Sorry for an answer that might not be as satisfying as one based on "hard science"; but I think it fits well the spirit of the franchise, whose one aspect is to warn against the dangers of letting private companies - with all the inefficiencies and dishonesties they bring along - handle such important things as Nature, Life, Evolution, ..., without any sort of external control.

In the beginning of the film, Claire says that a man wearing a Jurassic Park shirt was poor taste. I think that all of the employees at Jurassic World have a sincere respect for all of the men who died in the original park in 1993. They left the park alone and abandoned for the men who had died there to rest in peace.