Because if you're playing with a keyboard (or some other device that doesnt have analog input), it's almost impossible not lock up your brakes, especially if you want to play with hard sensitivity on the brakes.
I plAY without ABS and TC with my xbox controller and i do just fine on both career and MP races. Force feedback doesnt really matter much then. Its all about practice. ABS and TC are added to the game just to get new gamers or new "drivers" a feel for the car after that you can start turning them off one by one.