I also always wonder this, as it constantly seems like the only people I know who care are people who have gone out of their way to study UI; everyone else seems to find bespoke UIs "fun". It certainly doesn't seem to have hurt game developers much that every game has an unrelated UI..
Also desktop cross platform native GUIs. Programmers always complain about this, but most users are on windows and for them the GUI is just going to be ugly. No user is going to care that it is native.
