Because macs are terrible platforms for games. They have been very low end for a long time (m1 notwithstanding), and they have been killing off opengl, the only cross platform rendering API (before vulkan, which they don't support). Also their insistence on breaking changes means your back catalog needs constant maintenance. That's normal for app developers, but not gamedev. Oh, and if you do make the port, they will be about 1% of your users. Or less. So, to summarize, mac support is expensive, difficult, and not profitable. Should we still do it? I tend to think you're better of spending your time on linux support.
Maybe MacOS isn't a good push for gaming for either developers or Apple. I definitely think iOS is. The Apple Arcade Subscription plan seems to be part of that for gaming. I've seen a lot of people on the subway and even at work sometimes playing mobile games on their iOS device, from Call of Duty Mobile to racing games to tower defense.
I imagine when Apple expands their desktop and laptop lineup to M1 chips, it's going to include many of the games that are available from their mobile catalog.
