Apart from the vast majority of PC gamers having Windows on their PC's sure.
But I see your point
The sad thing is that Microsoft have been promising more support and involvement in PC gaming, and they do nothing.
Additionally though, we're seeing a big shift to other platforms being able to play the same sort of games that were usually restricted to a Windows environment, too. Which really you'd think would have given Microsoft a bit of a kick up the arse, but still nothing.
Developers do need to recognise the PC market more, however games aren't ported. When people talk about "ports" they actually mean poorly developed PC builds, as you can't actually "port" a game. You have to compile a build specifically for each platform.
What happens is that they compile a build for PC, and then do the barebones with it, not ensuring it takes advantage of the options available for PC users.
You got it right though, they would make more money just by investing that little bit more time. The stuff they often neglect aren't really things that would take much development time to address.
