Why do people insist on quad core cpu?

I built my own PC. I have an ageing Athlon64 x2 6000+ cpu clocked at 3.0ghz. A nice abit an-m2 motherboard. An 8800GT graphic card with Arctic Cooling Accelero AC-S1 rev 2 Radical high performance pive cooler x4 heatpipes and fan connected. This is clocked at GPU clock 650 mhz, memory is 1900 mhz, and shader at 1620 mhz. All my games I play, like call of duty 4, oblivion etc, I play them all at 1680x1050, with AF at x16, and AA at x4. Games run smoothly. So why do people insist on me getting a quad core. Don't they know most games are based on single core cpu's. Only a few are started to even use two cores. If I had a quad it would be a waste of my money, because only two of the cores would ever be used. I do not encode from avi to dvd. So why do people I talk to tell me to get a quad, and even upgrade my graphic card. Even doing that the games would look no different. Maybe a few extra frames a second, but come on, will I really notice a difference from the smooth gameplay I have already? I know the score with pc's etc. I was just wondering on your thoughts about the subject of quad. Is it really worth getting? I look forward to your replys.