How big that market is? Among established apple users? MacBook Air potential buyers? Hardware is there but where would the software go? AMD Intel NVIDIA are also innovating in its own field, and they are very much like the idea of ARM-based stuff in their core design. Apple has the lead at the moment, but what would happen if ARM becomes the norm of consumer electronics market?
I dunno what Nintendo or Steam trying to do here on the Mac side, especially after Steam releasing their own mobile gaming hardware based off of PC. They are also competing the gaming market. To them, Linux probably makes way more sense than macOS simply because of how much freedom they have on developing games on Linux.
On a side note, someone who cam easily afford $6100 on a maxed out MacBook Pro prolly don’t have any time to play any game anyways, and those who do would just buy MacBook Air instead, which is not going to be a powerhouse. How complex the game could be with that hardware in mind? And devs wont bother targeting 32 core GPU for games either.