As an example, I'm not an Xbox owner, but I do have a gaming PC. If Microsoft didn't bring out their exclusives for PC, I wouldn't buy them.
But since Quantum Break, for example, is coming out for PC, Microsoft will (most likely) have an extra game sold, which is also played on one of their platforms (Windows).
So I don't think it hurts Microsoft that much to release their games on PC. Not everyone owns a gaming PC, and the people that want an Xbox one, or already have one, don't need to buy a PC to play Microsofts exclusives.
A PS4 owner would have to get either a capable PC or an Xbox One to play those games, buying into Microsofts eco system, and that is all they want.
Platforms: Wii U, New 3DS, PS4, PC
currently playing:
-Yoshi's Wooly World
-Pokemon X
-Fire Emblem Fates
Zone: Europe (Germany)