When you think about it you realise how disgustingly clever the system is. They dont care about your health, but will probably keep 'hard drugs' illegal because they fear their workforce of taxpayers dropping out and not paying for their existence.
Hemp is another example, but has been kept out of circulation I suspect because of its many varied uses that can't be patented due to it being 'natural'.
The governments and corporations work hand in glove to keep taxpayers noses against the grindstone. Work for them, buy products from them, pay sales tax and payroll tax, take orders from them and fund corporations to be able to pay off government to make sure they can continue to pay your low wages, whilst making billions in revenue.
About 20 years ago I knew someone who worked for a cigarette manufacturer. He explained they had already made a run of cannabis cigarettes in expectation of laws being relaxed. Obviously they did not get the laws they wanted then and had to destroy the batch, but you can just bet that as smoking decreases, they will continue to push for them being the only 'trusted source' of distribution and all of a sudden, like the switch being flicked, for no apparent reason they will become legal (and have a nice tax on them no doubt).