You're so obviously correct in this. TBH I think the only reason the term "users" come up when it comes to isolating programmes from one another is because that was the only hammer Unix had, so it was coopted. The original point stands, the actual multi-user aspect is completely secondary and unnecessary to 90% of people. I'm the only person who uses my computer, but still I want to be able to isolate application 1 from application 2.