Probably because the Mac was a work platform, the Mac OSX being designed to allow users to navigate operating systems to do what they are supposed to.No one who is even a little serious about gaming does. That’s true.
Its false to say no one who is a little serious about gaming does...as I know of many professionals involved in games production who are using Macs both in narrative design, coding and all aspects of game construction and production.
Now Apple might have been late on the scene with the amount of games available, but that is changing rapidly.