This is probably controversial but my guess here is this; The bulk of the developer cohort doing most of the work in Linux userland these days cut their teeth on Windows, it is their internal standard of a "good developer OS experience" so when they build new things, they have that model as "good" in their mind.
The challenge continues to be software. If you are using the packages in FreeBSD (or other xBSD derivatives) it is not uncommon to see "package xyz does not have an active maintainer so it may break, if you're interested in becoming the maintainer go here ..." Not enough people to cover all the things that are pumped into the Linux ecosystem everyday.
And it is a bit too much work to re-create the old Sun Microsystems of old where the kernel and the core UNIX user land tools from BSD were combined with a bespoke window system, compiler suite, and hardware specific system libraries to make a product. Granted it was fewer than 1200 software people all told, when SunOS 4.x came out but they were all working for market salaries on the project full time. That's like 10 - 20 million dollars a year, not something you're going to do "for free in your spare time."
I'm not really sure how it resolves over time.