Programmers do stuff for free, all the time. People also donate to foundations so some programmers can be paid to make free stuff. It's how we got the Linux desktop as we know it.
Programmers often stop worrying about the details once they're satisfied, though, and there are a lot of details. Yes we could add thumbnails to the file picker, but we also need to support Nvidia hardware and the archive application is missing a few much more interesting compression formats, plus there are a bazillion logged bugs that actually crash software rather than being a minor inconvenience.
In theory someone could set up a collective of programmers, designers, and translators to create a usable Linux desktop for the Windows 10 refugees, but it'll require a lot of effort from a lot of volunteers and a lot of people who happen to share the same principles and preferences.
ChromeOS works because there's a single entity that can hire a small group of designers to tell an army of programmers what they want everything to look and work like.
There are actually projects and companies that fork ChromeOS, but they're pretty small and once Google stops maintaining the OS they're going to collapse pretty quickly.