There is no such thing as a "drug"
Either the stuff grows naturally and is just enhancing your state of mind, or its a manufactured good originally made to cure things or be used as a painkiller. I think the only drug that has ever been manufacterd to cause halucinations on purpose is LSD..and that was a swiss doctor who had to much time on his hands.
On Topic :
Why do people do drugs ?
1. To escape from reality, which is usually boring as fuck.
2. To reach a higher state of mind
^ these are valid reasons to do drugs, i encourage everyone to try plants that naturally grow at least once. Even if you're a fucking christian you should appreciate gods creation ffs.
3. Peer Pressure, never ever ever do something you dont want to do because your pals do it, if you want to try something, get something, ring up your best friend to keep watch over you ( even for weed ) and see if you enjoy it.
Oh yea, side note, don't touch the hard drugs like chrystal meth or heroine or whatever drug dealers mix up to make a quick buck out of your death.
These things dont register as a drug to me, its like a dealer hedgefond to certain death for its consumers.