The issue is software library related: they'd have to pay Microsoft a bunch of money find a way to get Direct X to work on their system. Granted there are a number of libraries that don't use Direct X, but they mostly use OpenGL, which is also not very well implemented on Mac OS. Blizzard games are pretty much the only exception, and they've sort of dropped that in Overwatch.
Some of this is fixable, but not a priority as long as Direct X is blocking them from a good chunk of the market. The real solution is to just dual boot into Windows for PC games. Or depend on the handful of ports that use Cider + OpenGL in the background and run slower with more RAM usage.
