Ah, but that's the rub, isn't it? Druggies will inevitably be a burden on society. You cannot remove all safety nets because there are plenty of non-users who will scream their lungs out about "fairness", "compassion", "humane treatment", etc. It is politically impossible to push something through when the socialists and the religious join on a certain issue. And complete legalization is bound to increase the number of druggies, at least in the first decade or so.
There's a difference between 'druggies' and 'drug users'. Actually, thinking about it, I'd say there's four classes:
Non-Users - Can be a drain on society, but odds are low
Users - Still not a problem
Functional Addicts - As long as they can get their drug they're functional. Almost like a diabetic and insulin.
Nonfunctional addicts - a definite drain on society, and they want their drugs, but can't support themselves and their habit.
Going by historical data, the nonfunctional addict, IE 'druggie' rate has remained pretty much constant through prohibition and the WoD. So it's actually fairly unlikely that legalization would result in an explosion of druggies - especially for something like MJ.
Also, consider the effects on criminality. Now you have more druggies trying to get their fix. Yes, the drugs are available and probably far cheaper, but when they quit their jobs over drugs, who will pay for their living and habit? So, criminality increases. The common citizen will feel the pinch.
They get caught and thrown in a drug-free jail to detox. Just like drunks who commit crimes to get their fix. Don't want to detox the hard way? Either keep your job(or any job) and do it legally or check yourself into a treatment clinic.
You simultaneously have to remove all restrictions on gun carry (a good thing) but will end up with a society where druggies and armed citizens shoot it out in the streets far more often than now. That will mean that a bunch of laws about justifiable homicide will have to be changed as well, the bottom line being much higher mortality among druggies (probably a good thing) but also among civilians (a bad thing). Then again you hit the above argument about bleeding hearts, and you end up back at square one.
Other areas have legalized drugs and found that the rate doesn't increase? Amsterdam is an exemption because it was a ghettoization of drug legality - users and addicts migrated there, artificially raising the concentration.
That's why a compromise is probably better - the division between soft and hard drugs. Soft drugs legalization will empty a lot of space in our legal system and prisons as well, when a bunch of local yokels do not get thrown in jail over a bag of grass.
How do you define 'soft' vs 'hard'? Alcohol, by most definitions, would end up in the hard category, while tobacco is one of the most addictive drugs out there. While I support full legalization of all the stuff, I wouldn't mind a gradual legalization process.