Seems like a sensible step and possibly free up public services a little for other things? Legalising and taxing feels like a good thing too, but maybe I'm being naieve. Overall though, good for society.
My biggest worry, and it's such a selfish worry, is how it affects me. I've had neighbours (terrace and semi-detached) who smoke weed and it causes everyone's house to stink. It's a shitty experience and something you can't do a lot about. Would that happen more and more with decriminalisation/legalisation? You can use whatever substances you like, but should I be affected by that choice?
I'm not sure I trust people to consider others, drugs or not.
Perhaps it's the case that if there are specific 'safe-use' spaces, people won't have to do such things in their own home and instead have other places to do - if people have somewhere where they can safely consume drugs and have medical help/supervision then theoretically the need to do that in private becomes unnecessary?
I see your point however as I only have a 20 minute daily commute and yet still often come across the smell of weed once or twice!