I've never called up a game company for tech support. In fact, I've never called anyone for tech support for any game. I don't know anyone who has either and I know a lot of gamers.
AFAIK, Half-life had a Direct3D and OpenGL renderer and so it would not have been too difficult to port the game engine to other architectures, especially Macs.
It would have brought them more sales, it would have cost them very little if the code was portable in the first place, a little more if it wasn't. The demand clearly is there, so they definitely lost a lot pf potential sales.