Yes, of course, or you wouldn't have the ability to do it at all. But Apple cares more about it's users and the experiences they users have, and things like GateKeeper help them sell users on a safer, walled experience. As an Apple developer (in that I've paid for a license, not Apple-employed) with parents and a grandparent who have a Mac, I much prefer simply telling them to only install stuff from the App Store and not worrying about downloading and running anything from the general Internet.
Yes, of course, or you wouldn't have the ability to do it at all. But Apple cares more about it's users and the experiences they users have, and things like GateKeeper help them sell users on a safer, walled experience. As an Apple developer (in that I've paid for a license, not Apple-employed) with parents and a grandparent who have a Mac, I much prefer simply telling them to only install stuff from the App Store and not worrying about downloading and running anything from the general Internet.