you should learn about systems software... they may be 'vanishingly small' but they're there in the foundations of the entire computing stack. done once, a long time ago, and used by all ever since.
just the most basics: but there are (sadly were) more: https://en.wikipedia.org/wiki/Glibc
They're not written in stone. They still change and evolve.
I reject a future in which all software works as a subscription based service; this is just more taxes (in principle)
I see society going down this path and there are no good reasons for this at all (it is just double then triple then mutliplefold taxation on activity; and what for? so that few lucky persons collect rent forever?).
¯\_(ツ)_/¯