The vast majority of desktop Linux users run Ubuntu (initial motto: Linux for human beings). So one may argue the literal opposite of what you wrote, in that if Canonical didn't invest into making a Linux distro that's accessible to normal people, it wouldn't have the relevance it now does. On top of that, Linux has (or had) a number of clear advantages over Windows that dwarf the presumed upsides of compiling everything from source vs. downloading builds.

There's not much of an argument for adopting obscure niche practices for their own sake

The rather large giant collosal planet sized argument that you somehow missed despite that, is that every single thing that you consider good and normal today doesn't exist except for the fact that at one point it was the obscure niche thing that annoyed intolerant "normal" people.

Linux was obscure and niche for a very long time before Ubuntu existed and Ubuntu only existed because someone bothered to use and develop Linux when it wasn't normal.

The Ubuntu users are only there because after they had told the rest of us how silly we were for using Linux they eventually had to use it themselves for work.

Now we're going to listen to that sort of stuff again without rolling our eyes? ....