That's a great point. At any point in time there are already dozens of processes running, of which only a fraction are tied to a GUI. Even GUI apps are currently resorting to launching multiple processes. For example, Firefox announced last year their new site isolation security architecture where they load each site as an independent process.

https://hacks.mozilla.org/2021/05/introducing-firefox-new-si...

Also, here's a link to a recent HN discussion on Firefox's recent announcement.

https://news.ycombinator.com/item?id=31355857