I used to be a PC gamer, but:
1) The majority of my friends are console gamers now, like I am, and many of us were PC gamers -- or at least had PCs as well. THe #1 benefit to us on PC was playing online, but really, X-Box Live does that better for us now than the PC and a bunch of apps and programs ever did.
2) Price, which also matters for many of my friends. Most of us used to have new PCs, but now, most of us use laptops and tablets for regular computer use.. like using Facebook and stuff, and so our desktop PCs are dated an dless used. I use my desktop for work, but even then, I still do a lot of work on my less powered laptop.
3) The necessity to upgrade. When I do play PC games, I play games from 5+ years ago, or games with lower demands... Sure, I could probably get better graphics, etc., but it's a pain for me.
4) The hassle of playing PC games, and this may not be the case anymore, but for quite a while, when the latest generation of consoles game out... all I needed to do was put in a disc and the game loaded and I was playing. NO worries about "will my system handle it," or "I wonder if I can tweek this config to get better settings," or "nuts, I'm running at only 25 FPS while my friends are all running at 60fps.. and they have an advantage, etc." I know that the experience is the same for me and pretty much everybody else.
Now, some of these may be myths... But right now, I don't need a reason to stay from PC gaming, I need a reason to come back to PC gaming, and there isn't a compelling one for me. The biggest one, though, is #1... the social component that is so expertly built into my 360 and my close group of friends. The 360 has been cheap enough for a few years now that all of my guy friends have one, and so whenever a big multuplayer game comes out like CoD, or even the multiplayer in RDR, it's like a big friend reunion for a few weeks, as like every night 8 - 12 of my friends are on XBL, playing games, chappin it up, drinking beers and having a blast. With only 2 or 3 having good enough PCs and then, maybe not even having a good enough PC for the *next* big game, that social component doesn't exist for us.