I see your point, but unfortunately, there’s lots of proprietary old software that has been abandoned by the original company (Either because they went out of business or just moved on) that’s still in active use and the source never released.

There was just an article on Lemmy a few weeks ago on how multi-million dollar research facilities still have to use ancient software to run critical scientific machines. Although in that particular case they had to maintain old PCs as well because of proprietary drivers