Apple could but they're not interested in non-native games, they want native ports or nothing. As I discussed a few posts over, Apple went to the trouble of developing a DirectX compatibility layer, but then told game developers they're not allowed to use it for anything besides evaluating whether their game would run well enough on Mac hardware. If they go ahead with a port then Apple still expects them to do it all the hard way.
It's textbook "perfect is the enemy of good" because yeah, compatibility layers have overhead, native is better, but if you insist on native everything but can't get devs on board then you just end up with no games.
Compare Steam Machine (2014) to Steam Machine (2026). The difference this time around is Proton support, and you can pretty easily see the hype on the internet for the new version, even after the original version was mocked relentlessly in some circles for having "no games."
Well, some games like Civ V still manage to work! But they actually had to port it to 64-bit, otherwise it'd have the fate of all other 32-bit macOS games unfortunately...
Also, how could Apple kill the old software that is better than the new, if it doesn't control the emulation? This way they don't have to even have 10% of the features to force you to buy again.
It's textbook "perfect is the enemy of good" because yeah, compatibility layers have overhead, native is better, but if you insist on native everything but can't get devs on board then you just end up with no games.