This is a pointless discussion, with a significant number of users wanting each side. It's also a silly discussion given that Emacs is perhaps the most configurable software on the planet.

Personally, on multiple occasions, I've been frustrated when upgrading some (non-Emacs) SW and have it behave differently because they suddenly decided to make using xdg the default and then having to waste time finding a way to revert that behavior.

This isn't a problem unique to Emacs.

I'm sure if Emacs seriously started losing lots of users, they'll change the defaults to attract some. Until then, the developers (and most chronic users) simply don't care.