Why is a carry lookahead adder considered better than ripple-carry in the worst case?

Based on everything I have read on the topic of carry-lookahead adders, it seems to me that it merely improves the average case. The worst case of 0111111...111 + 1 still seems to have equal execution time to that of a ripple-carry adder. Given that we have to handle the worst case in CPUs, why is this an improvement over the ripple-carry?