To most people the fact that they can't get halo on PS4 is enough for them to buy an Xbox if they want to play Halo and the PC is out of the question because
1. The initial cost is downright expensive and I say that as someone who has a PC with an i56600k and gtx 1070
2. They aren't going to want to build the PC because it takes forever and it may look hard to someone who's never tried it
3. People don't want a PC in their living room they want slim devices they can fit under their cabinet and I mean SLIM. Remember how much crap the 2013 xbox one got for looking like a VCR player? People thought it was too big.