Is not that people are bias toward AMD, is just that AMD is better for gaming and single processing. Benchmarks have proven that. I will admit that there are certain areas where AMD cannot compete with an Intel. I have two computers. One is running with an Athlon 4000+ and the other running 2.8 Ghz. I tested both rigs by torturing them by running photoshop, burning DVD, winamp, using AIM, and playing a game at the same time. The Intel processor certainly alt tab faster and there was less delay than the athlon processor.
Most people choose athlon because it is significantly cheaper and most people nowaday plays computer games or just do some simple multi-tasks on their computer. You see the Athlon 3200+ is currently 199 in newegg and the Pentium 630 is 225. Price does make a difference, and Athlons are much easier to overclock from my own experience.