Because vengeance as a central tenet in justice systems is straight from the Hammurabi code and unfit for the modern world. If your source is the Bible, I'll agree to disagree.

If you want a legal system that treats citizens fairly, you want one focused on rehabilitation. Locking someone up simply doesn't accomplish that goal. Dehumanising prisoners doesn't either.

What's more, crime is a proxy for socio-economic status, which given the greater inequality in the US, partly explains the disparity with other developed nations.