Remember, what you are talking about is only one application of hash functions. In the world of crypto, speed becomes very important in things like MACs and sig

Remember, what you are talking about is only one application of hash functions. In the world of crypto, speed becomes very important in things like MACs and signatures. There are a ton of other uses for hash functions that are not crypto-related too! Besides, even when using a "fast" hash function for password storage, you can always just increase the number of rounds to compensate.