Drifting is slower if you're racing on a road surface. You switch over to gravel, dirt, or snow though, and drifting helps. The main benifit in the loose stuff is that you can get your car pointing in the correct direction earlier and adjust your trajectory through the turn with the throttle. If you try the classic racing line in the loose stuff and you're going to fast through the turn, you'll just slide straight off. If you go in too fast while going through sideways rally car style, you can use your throttle to keep you on the road as the car is already pointing in the correct direction. Or something like that!