I like an occasional beer and had a bit of weed on a few occasions in my youth (not opposed to it now, just not my thing). Society would be 100% better off if neither existed (lower healthcare costs, fewer people in Jail, fewer people on income assistance, etc.). That being said, government has to deal with the the reality it has and not the one it wished it had.
I think with all of the things we know are not good (cigarettes, alcohol, drugs) it is a matter of coming up with the policy that is going to minimize harm ... you can sell it, tax it, and use the proceeds to fund programs or the bad guy can sell it and use the proceeds to fund their activities.
I think they should ban a lot more than strews (single use coffee cups come to mind). Around here there was a land fill. There was a constant debate about adding more cells ... they were running out of room and needed more space. This debate raged on for years. The municipality banned opaque garbage bags (you can have 1) ... the amount of garbage going to the landfill dropped so significantly that the landfill now had enough room for many years (something like 20 or 50).
