It's also one of the reasons users and proprietary software have been rare on Linux.
It may be why proprietary software is lagging, but I think most users prefer an OS level package manager. They just didn't know about them until the Appstore.
The Linux kernel is everywhere thanks to Torvalds (overly late in the opinions of some BSD devs) declaring the API/ABI sacrosanct, and holding the other kernel developers to that (much to the chagrin of some that want to do hail mary changes for sake of security or ego).
But the userspace above had been reimplemented again and again because the various libs and such are fundamentally unstable. In far too many cases you can even do a x.y.z+1 update without getting some kind of breakage.
Often because someone decided that spec adherence was more important than real life stability, and thus pushed a patch through that altered the API behavior to be more in line with a spec that nobody had complained about for a decade or more.
The Appstore works on phones and tablets because they are primarily consumption-only devices, and because users are not given any other choice (also, the installer/uninstaller model has a lot of its own suck). I don't know about you, but that's not what I want out of personal computing.
Nobody is complaining that applications are in a central location.