I think the 4-banger race thing became so popular because Detroit stopped putting out affordable rear drive V8 cars. No cheap ones at all, and assuming you avoided the ULTRA-HEAVY ones that left you with 2 choices, Camaros and Mustangs.
It IS sort of silly though to buy a $17,000 car and then spend $15,000 more to make it almost on par with a $25,000 car.
I do like suspension and handling mods though, if I was into that scene then that is all I would do, suspension, handling, and brakes. Juicing up the engine just to lose to stock camaros is just silly, and its only useful on the street if you want to drive like a moron, which you cans till do cheaper with a stock Camaro or Mustang.