> This isn't entirely accurate. Plenty of apps run Terminal commands in the background (for some reason).

A lot do it because sometimes there is no convenient library wrapping what they are trying to check or execute that they are aware of, and running a cli command is generally cheap unless you are doing it in a tight loop. A lot of the time this is “it'll do until I find the right library or bindings” code that should have been fixed before release, but it isn't all as bad as running top as you describe.