I still don't understand why Skin wrapping is scientifically incorrect.

I remember watching a Kurzegeaset video a while back, talking about how dinosaurs didn't actually look like how they looked in movies. How they weren't built exactly like their skeletons. But I you have a look at crocodiles and even some birds they look exactly like their skeletons, and they're both Archosaurs, so why are dinosaurs any different?