Okay, so I can go from getting 80-120 FPS in most games (or ~180-200 in Q3) to getting 90-140 FPS. Why? It already looks awesome, it already plays smooth. 10-20 FPS doesn't make much difference when you are already getting more than you need for smooth play.
Same thing with my car. Why would I want to tweak it (and possibly damage something) when it already smokes most cars in the curves and can do 0-60 really fast (around 7 seconds). I could drop a turbo in it, an intake kit, or maybe an exhaust system and REALLY smoke people on takeoff, but I don't need to. That isn't where I get my fun. I didn't buy the car because of what kind of performance I could get out of it. I bought it because it's fun to drive.
Eh...this is going to go nowhere...shall we agree to disagree?