Because of casual people. Not everybody has the same skills for driving. I can deal with no TCS (I never run with it unless I decide to cruise realistically so with it on in modern cars) and so can other skilled players, but others can't drive very well without it. It's an option regardless, so I don't see why you're bothered by it.If this is a real driving simulator, why can we use in Gran Turismo driving aids like TC and ABS that never existed in cars from the 70's, 80's or before?
Because it's a game, is the simple answer.