I've used an app store (or rather an 'apt store') since 1999, it's the reason I moved from redhat to debian in the first place.
I'm not sure that "desktop computers" as we know it were around in the 60s (I certainly wasn't), but in the early 90s software tended to come from floppy disks, before that it was a C90 cassette on a spectrum.
Microsoft Store and Valve Steam do not contain (shock!) browsers, office, tools, etc. That I believe is a distinction between distribution and store - "store" agenda is not aligned with users.
