> Of course there are scenarios that require 3 life sentences (e.g. serial/psychopathic killers), but they really are rare

This is mostly a problem with "sentence stacking" in U.S., which I absolutely think is not the "right balance" for punishing someone in a society. Not to mention how much it's been abused by prosecutors who "throw the book" at the people they want to make an example and essentially force them into plea deals, just so the prosecutors can score another "win."