Let's see:

• There is already Steam for Mac, which a great catalog and sales.
• The only appeal of an App Store game is cross-platform... in Apple devices.
• Consoles (with controls) are cheaper than any Apple product compatible with AAA games. (This includes the Steam Deck).
• There are no platform-selling exclusives.
• There is no exclusive hardware features.
• Major most-played games are not available OOTB: PUBG, Roblox, Rocket League, Genshin Impact, Apex Legends, Call of Duty, CSGO2.

Yeah, I get the sentiment: why. But Apple has to start with something, and if they want people to buy games they will need a bigger catalog, and for that they need to keep their porting tools easier to implement.