We know that drugs are treated in different ways, there are legal but subject to medical control, legal free-selling (tobacco and alcohol) and there are the ones in the hands of criminal circuits. However, legality is not decided on the basis of the seriousness of drug addiction, because ya, alcohol is the most dangerous drug, the most used and has the most social risks like violence, car accidents and etc.. but no one ponders its ban because it would increase the harm like some dudes said before.
In Portugal drugs have been decriminalised and you won’t go to jail for buying weed (or any other type of drugs). Instead, the "sentence" will be anything from absolutely nothing to having to attend a rehabilitation program. The police generally turn a blind eye to someone smoking a joint and, unless you do it in their face or carrying a considerable amount like more than 25 g of weed or 5 g of hash (which is more than what most people need to carry on them at any given time), they’re usually not interested in pressing charges.
When it comes to actually buying weed, or any other type of drugs, you still have to hit the streets to find a dealer. It’s somewhat easier because you will be approached by dealers. But it's still illegal to grow marijuana.
I heard somewhere that in 2016, Colorado generated something like more than $1.3 billion in revenue from marijuana sales. Nearly $200 million of that for taxes, it was so much that the government has even considered giving local citizens a rebate.
Even though drugs have been decriminalised, thank zeus, Portugal isn’t a stoner paradise like some dudes think it is, unless you're french. Therefore, experience and history indicate that drug control is better than being handled clandestinely.