I'm still amazed they never entered the console space with how closed a system they have.
They sort of did, with the AppleTV (which is no slouch either.) But Apple doesn't really have anyone who cares or really gets gaming—they didn't support the iOS App Store enough that "premium" games could really make it work, they let their online services die, and they didn't pack in a useful controller.
It's a shame, because they could provide a pretty compelling product in the space. But they can't even be bothered to half-ass it. I don't think Apple particularly cares though, because casual games still make them money hand over fist with a lot less effort.
The question is,
Why do I need all this speed on my cell phone when it seems mostly unnecessary?
Leaving aside the potential for more graceful aging, a lot of that power is going into 'invisible' stuff like computational photography and background processes. But there are also people who are legitimately using their phones and tablets for 'real' work, not just consuming content and posting on social media, and the speed obviously benefits them there.