No, it's Valve just not giving a hoot.

People don't seem to (want to) remember, but before the run-up to the Steam Deck, Valve was really coasting.

Big Picture was riddled with bugs. Controller configuration was riddled with bugs. The Steam in-game overlay was terrible, and had been terrible for years. Their internal browser was a custom stripped down 5+ years old Electron or Chromium Embedded Framework monstrosity, begging to be exploited somehow. Chat and voice chat was terrible, didn't scale properly and was missing many of the features of things like Discord.

And things had been stagnant like that for 7 years, if not more. Their built-in browser and chat functions are still terrible. In regards to chat and voice, I hope they cave and add Discord integration, so we finally have one service for PC, Xbox and Playstation.

Their store was and is still all webviews, the pages themselves are terribly optimized and many of them aren't even controllable on the Deck without touch. You read that right, the Big Picture cursor doesn't work on some store pages, which renders them unusable on handhelds without a touchscreen / hardware (emulated) mouse.

Steam is miles ahead of the Epic or GoG UX, but it still has lots of warts.

Steam Input controller bind customization is off-the-map nuts with how broad it is now though, major props for that. And the 'new' Big Picture is a vast improvement.