I would say the same about custodial sentences, if they had any deterrent we would have empty prisons. We just lock people up because it keeps jo public happy and avoids dealing with the real problems.You may as well say the same about custodial sentences.Don't see that abusing the abused solves anything.
It's called justice.
Revenge is a natural response to human emotion, does not justify it though, justice should be based on fact and reasoning, not emotion.
prison isn't just a deterrent, it's purpose is to remove criminals from society too, as some people are just bent on committing crimes.