You can fine folks for smoking cigarettes in places it is not allowed. Including many/most public places. I'm curious why you think that couldn't be done with pot?

Public drunkenness is also not without consequences. By and large, you solve a lot of those not by focusing on stiffer penalties for folks doing them, but by giving them a place that they can do so legally. Is akin to a skate park. Good skate parks go a long long way to getting skateboards off of sidewalks.