It's because of the way development works. The actual developers love tools and high quality APIs like Metal, but their bosses are idiots who only care about money and say dumb things like "Hey, lets use <dumb technology choice> to save ourselves lots of money"
Games is always going to be a problem for the Mac, because the hardware is console performant, but high end Gaming PC with top of the range GPU in price.
Who's the market for that - people who can afford the expensive mac, but not the console or dedicated gaming pc? People who want to game occasionally... are they worth developing for?
Back when I worked in games, even the PC port was generally a labour of love where the higher ups would be all "Who cares about the PC, they have powerful hardware so don't waste time optimising the PC port when you should be spending your time on the Playstation version"
Hence Microsoft's value proposition for doing Windows / Xbox as the same codebase.
Mac ports are similar where there is literally a 0% chance that your boss is going to come and say "Hey let's make a Mac version" unless someone at Apple has given them a suitcase full of money (and even then it would probably involve doing the bare minimum). It would essentially be up to an individual developer to prototype a Mac port and literally hand it to the higher ups and say "Hey, can we have a Mac version, I've basically ported the game already and all you have to do is accept the free money". That's why these tools are such a massive game-changer.
It still leaves open who the target market is - people who don't want an extra device (aside from their iPad, iPhone, Airpods, Vision Pro etc).
It's also why I don't work in games anymore because it's the most dysfunctional industry on the planet.
I'll credit Apple this - their money-up-front payment model to get games made for their service is a MUCH better model than traditional game financing.