You are right, Apple could do it, people would love it, but they won't.
Simply as those at the top are not interested in that direction.
Such a shame
I fully agree that Apple has little interest in gaming (much to their detriment), but the situation is more complicated than that; Apple would have to pour massive resources into achieving "gaming parity" with PCs due to software optimization alone. The same title running under Windows will perform much better than the Mac version on the identical piece of hardware. Sometimes the difference is marginally tolerable (Divinity Original Sin, which runs maybe 1.5x faster in Windows) and sometimes it's unbearable (Pillars of Eternity, which seems to run at least 4x times faster in Windows - which is a shocker since this game should be very light in terms of CPU/GPU resource requirements). If forced to pull a number out of my arse I would say to assume you will get around 1/2 the performance out of the Mac version of a game. That means, if Apple really wanted to take on gaming in a serious manner they would have to produce hardware with double the performance of Windows PCs just to achieve performance parity. Is this really Apple's fault? Well, no, there are a lot of places to point fingers (poor programmers producing poor ports, rushed ports, Microshaft killing Open GL with their Direct X initiative way back when it looked like cross-platform gaming would become a reality, etc.), but it is the unfortunate reality of the situation.
It seems to me Apple should be promoting, not preventing, game stream from Gaming PCs to iThings and Macs. ("Got a gaming PC in your home? Stream your games to any Apple TV, iPad, iPhone, or Mac in your home seamlessly and easily!")