One would've expected one of the many desktop-oriented distros (some with considerable funding, even) to have tackled these things already, but somehow desktop Linux has been stuck in the awkward midway of "it technically works, just learn to live with the rough edges" until finally Valve took initiative. Go figure.
It's not just Valve taking the initiative. It's mostly because Windows has become increasingly hostile and just plain horrible over the years. They'll be writing textbooks on how badly Microsoft screwed up their operating system.
That isn't it. Generally whatever the majority of users tend to use that where the majority of focus goes.
The vast majority of people that were using Linux on the desktop before 2015 were either hobbyists, developers or people that didn't want to run proprietary software for whatever reason.
These people generally didn't care about a lot of fancy tech mentioned. So this stuff didn't get fixed.
There's far more of that, starting with the lack of a stable ABI in gnu/linux distros. Eventually Valve or Google (with Android) are gonna swoop in with a user-friendly, targetable by devs OS that's actually a single platform
Please don't erase all the groundwork they've done over the years to make it possible for these later enhancements to happen. It wasn't like they were twiddling their thumbs this whole time!