DRUGS - why are some allowed - others not allowed?

Bayer in the 1890's had an in house tester try out two new drugs Aspirin and Heroin. the tester's conclusion was that heroin was quite good but Aspirin was quite dangerous.
(Bayer trademarked "heroin" and marketed it as a cough suppressant and non-addictive substitute for morphine from 1898 to 1910)(wiki).

I used to take ibroprofen, great stuff for chronic bad back. But it's side effects put me off it.
I don't drink or smoke. but consider drug use as a personal choice.
If someone wants to take drugs I think they should be able to do so safely with medical advice.
Making drugs illegal means you are open to corrupted products.
No consistency in what you are taking.

Vaping is in the news - nicotine is an allowed drug, paracetamol, cocodamol ? all kill people.

As far as i can see they don't want drugs that chill you out and makes you non productive. If the drug is too cheap you won't go out and work for it? If you can grow your own. where's the profit for the companies.

so the drugs are available to keep you moving - painkillers so you can work. drugs that take the edge off so you can move smoother.

I used to move furniture and i had to pack a room in a basement of an auction house - all through the morning I struggled away and was pretty unhappy and laboured hard at it? Lunch time came and my fellow worker and myself went over to the local pub for a Guinness or two. After lunch I felt like superman. I was moving furniture as if it was Styrofoam.  That was a good drug choice.