There is no moral or ethical justification for the death penalty. There also is no financial incentive for it. It actually costs more to hold a prisoner on death row than it does to confine them with a life sentence. The continuation of a death penalty with no moral or ethical justification is of particular concern. That leaves revenge, which is based in hate, as the only remaining plausible reason. Revenge as a motive breeds hate, resentment and further episodes of revenge, repetitively, ad nauseum. If you don’t understand why there is no moral or ethical justification for a death penalty you are highly unlikely to understand the explanation.