I think the big issue is that the user doesn't have a choice in many cases. Windows obviously doesn't give the user a choice, they made the start menu much shittier and you had to live with it or go away. Popular distributions like Ubuntu also focus on one desktop environment, and it's often not easy to switch (it's possible of course, but at least when I tried it a long time ago just installing a different desktop wasn't enough).

Making it easier to choose allows for much more experimentation. I'm using Niri right now, which certainly isn't something you can just give users as a default.