Neither smartphones nor Macs have been powerful or ergonomic enough to play current-generation games for decades. So the user base is almost entirely people who don’t play games.
For a developer, the juice is not worth the squeeze (and by far!). The platforms are challenging to port for and all that effort seems to result in near-zero sales. All ports seem to be almost guaranteed commercial failures.
My key point is that perhaps the platforms are now mature enough to develop for and Metal is alright. But they have not been for a long time and it’s a really bad market to target for a game developer.
Unless Apple funds your games like some other platforms do, it’s better to just blow the porting budget on something that’s at least fun. I haven’t heard of anyone’s game funded by Apple, but maybe it happens? These deals are rarely made public.
Chicken and the egg.
Just my opinion.