God had remorse at what he had done and made a covenant to never do it again*. One of the morals of the stories is that the means it would take to wipe evil off the earth isn't worth it.
Well, also, in the Biblical account, it was too late, they were all too far gone. I would argue it's not so bad now. :-) Imagine if your Mom sacrificed your older brother, and your Father was raping your sister, and ... Crypto in that light seems benign.
* at least that way