oil breaks down over time and use. when it does, it's viscosity goes down causing more friction in the engine. the more friction there is, the less power is made.
I know you can run **** parts for decades and not have a problem, but most people don't beat on their cars half as hard was most owners of "performance" cars do. The more you ask out of your car, the more you will have to give your car.
I'll be trying the new "Ea Nanofiber" Amsoil oil filter at my next oil change. Even with my discount I think they're about $12 or $13, but I don't really care.