re: So why don’t we legalize cannabis?

The Feds need to de-schedule it and then leave legalization and regulation up to the states, similar to how they handle alcohol. You would definitely see a dent in opioid abuse, and be able to clear out any cases and convictions involving simple, non-violent possession. Murders might drop a little simply because you'd likely have less drug deals gone bad.

There is no logical reason, in a country that has legal alcohol, to keep weed illegal. It's only the powerful lobbies that keep it illegal today.