Depends on an application. Plenty of applications have a legitimate reason to hook into global keyboard handlers, or otherwise instrument other applications or the system itself. Removing that capability would be crippling to the utility of a computer.

It sort of works in the mobile space (+/- accessibility services, which are the way to get that functionality if you need it), but that's only because mobile devices are consumption-oriented; there's only so much you can do with them, and they eschew utility in order to streamline you into being monetized by third-party services.