Because vast majority don't know much about skeletons in 3D except that it's used to drive animations at best. And the ones that do complain also know very little about skeletons as evident by their obsession of it as if it's so important that they are unique skeletons.
Newsflash, it's not important at all. I can use the same skeleton for 20 unique races and all of them having unique animations tied to it.
Most skeletons are generated through scripts and if you can reuse skeletons to speed up the rigging process you should absolutely do so because that means you have more time doing things with the skeleton rather than wasting time creating it.
https://www.cbr.com/assassins-creed-...etons-ubisoft/
As long as the skeleton is doing it's job, it's good. The less time they spend on making a skeleton. The better. More time for everything else.
Don't get me wrong, you can call them lazy for doing whatever and complain if they reuse animations but that has nothing to do with reusing a skeleton. Since you can copy animations from one rig to another if the bones are named correctly. And any rig that you copy over to another model still, most likely, requires work because the new model probably need new tools for certain animations tied to said model and it's details.