My guess is that it's because there are only so many ways to arrange cases of bones and reproductions of skeletons in a way that's visually interesting, compelling, and informational.
It's a small enough industry with expensive enough parts. There's probably exactly one and a half companies that make cases for uses like this that provide the furnishings for every natural History museum.
Oh, that makes all the sense in the world. You're probably right.
Even if it's a dozen companies making cases for every type of museum, zoo, and aquarium, it's probably going to be a little bit like Chromebooks where the vast majority of different options are going to look the same unless you stare at them right next to one another or are in the industry. Most industrial design ends up pretty samey because that's what people expect.
Sounds like there's a gap in the market for thematic archeological bone arrangement. Just imagine, a T-Rex skelly doing a kick flip off the back of a stegosaurus.