Fore me, it is because I have been gaming at 60+ FPS for decades now. In my earlier PC gaming days, I couldn't afford (read: my parents didn't care) the latest and greatest and so I would have to either sacrifice graphics quality, or framerate. I could usually find a good balance and as long as I was above 30fps, I was fine. Nowadays I do not have that problem and everything I play is at 60+.
For consoles, I am willing to take a framerate hit depending on the game as long as the graphics quality makes up for it and the framerate is locked and solid without dips. 30fps in many games is acceptable and very playable. But if it is a racing game or FPS or any other twitch style game, it has to be at least 60fps.
I just recently got a 144Hz G-Sync monitor and that buttery smoothness of it is awesome. I cannot go back now.







