For me, there are evenings when I am hacking away on a hobby project for 2 or 3 hours. Then suddenly just go, 'I wanna just veg out for another 2 hours then go to bed.' When I'm in that mood, I don't even want to be bothered changing machines. Just hit the steam icon and veg. Thats also bout the only time I end up gaming though, haha.
Last time I dual booted though, I remember why I didn't for along time. Did a Windows update, windows rebooted my computer and it did something with grub and I couldn't easily boot into linux anymore.