The war on drugs hasn't worked. People will always get off their faces, even in puritanical countries with death sentences attaches to alcohol/drug possession/dealing.
The problem with criminalising drugs are manifold. Otherwise decent people are, by definition, criminals. For an extreme view, look at incarceration rates in US....life, for a bit of weed. People wishing to use illegal drugs are forced to engage with criminals, sometimes leading to greater criminality and social harm.
Criminalising drugs leads to greater harm to the user and greater social harms. A crack/heroin addict (unless they have rich parents/trust fund) has to engage in criminality to fund their illegal habit. Women can be forced into prostitution as well as theft and burglary, making them far more likely to use up police resources, CJS resources and scarce prison resources. They also neglect their health in other ways, not eating properly leading to an expensive burden on the NHS.
An addict can often live a healthy, legal, purposeful and socially useful life IF a clean source of their chosen fix was available though cheap and legal channels.
Personally, I think hard drugs should be available on prescription from GPs, with attendant monitoring and healthcare. Certainly the overall cost would be way less than the current situation.
Privately, most if not all senior police agree, but the only thing preventing progress are reactionary attitudes from people who haven't done the thinking.