In my case it's because of cheap games and convenience.
Thanks to the numerous sales, games are a lot cheaper on PC and, on top of that, there are plenty stores/sites that give away free games. For example, 7 of my 11 games at UPlay and 12 of my 13 games at Origin were free, and I also have several on Steam.
Then there's convenience. I already spend a lot of time in front of my PC, so for me it's easier to just launch Steam or another platform and play with a couple of clicks.
Please excuse my bad English.
Currently gaming on a PC with an i5-4670k@stock (for now), 16Gb RAM 1600 MHz and a GTX 1070
Steam / Live / NNID : jonxiquet Add me if you want, but I'm a single player gamer.