Revenge is personal, whereas retribution is societal? They might be the same thing ! Still, it's an interesting point. Prison is revenge for the victims. You can also be retribution by society and the government. One is in response to an emotional desire, the other is a policy response. It's like you can punish your child to teach them a lesson, but not because you hate them.
Having the government do it also prevents blood feuds. If you exact revenge, the family might come back for revenge on you.