A fair question. There is actually a sizeable movement within American Christianity that fits within your expectations, calling for the end of the death penalty, visiting and ministering to prisoners, etc, however there is certainly a more dominant retributive aspect. I'm not qualified to fully answer your question, but I think a partial answer would involve remembering that Christianity overall explores the tension between mercy/forgiveness and justice/judgment (ex. Romans 11:22), and in the work to build a functioning society, some gravitate more easily towards one or the other...