Liquidity. Buying a car on credit is mostly stupid, but there are cases when it makes some sense. My last car loan was 3.54%. My combined accounts were earning ~8%. Paying cash in that case would be throwing away money. Well, throwing away money on top of wasting it on a car.
I can't speak for the other guy, but these high interest investments were available when I took out my car loan too. That's why I opted for the longer term loan.