For me its a number of things. Familiarity is one, i am just more use to playing games on a console with a controller, mouse and keyboard are just not an ideal setup for me. The game selection is more limited on PC's and outside of some FPS's, MMO, and strategy games (none of which are my favorite genres) all the games can be bought on consoles (Im more Final Fantasy then Elder Scrolls).
Cost is also a factor, $600 will get you a nice video card and while the graphics will always be better on PC for half of that (now any way) gets you a box with tons of built in features with out the hassle of Windows updates, viruses and drivers. There is also the factor of the console specific games that will never be available on a PC (the Sony/Nintendo first party games). After buying 3 consoles and two handhelds I really can't justify beefing up my PC to play a few games (likely already on something I own) just to have better graphics. Also could be that since I am a computer tech/network Admin I view PC's as more of an annoyance then something I have fun interacting with, lol