Someone can like something but not find it valuable enough to zap; and at least for me likes have become a way to discover people who saw and interacted with my notes, and it was the first spark to check out who those people were.
Still love zaps, and have different reaction to likes vs zaps, but I enjoy having the option to make myself present in someone’s notification via like so they know someone saw what they threw out into the ether.
Different degrees of interaction imo.