The difference with MacOS is that Mac once had a decent market share. Linux never had, and continues to not have it.
There are third party companies that only support MacOS, and work on porting games over to MacOS. Most game developers do not do it themselves because its not worth it for them. Ubisoft, EA and others do not usually build their own MacOS builds of games, they let someone else do it because its their business.
And those businesses as you might guess are very small businesses with very small revenues.