I think the proliferation of POSIX-like OSes is mostly down to OS projects wanting there to be useful software that can run on their OS, so they minimize/elimin

I think the proliferation of POSIX-like OSes is mostly down to OS projects wanting there to be useful software that can run on their OS, so they minimize/eliminate the work of porting. It has led to the phenomenon you describe though -- instead of thinking an OS is just too much work to port to, it might be thought of as being "wrong".