Who ever said drugs do not kill has never really used them much. While some drugs may not kill you directly, your behavior on drugs and your experiences when using them can kill you. For example, alcohol or weed may not kill you, but driving drunk can. LSD will not kill you, but walking through a window and falling 20 stories onto a concrete sidewalk probably will. Cocaine may not kill you, but driving 150mph into oncoming traffic on the highway can. Who ever does not believe in these scenarios must never tried those drugs.
Let me give you some of my own experience.
Please, please, please, do not do drugs!
I was never a "stoner" in the traditional sense of the word, in that I never smoked marijuana more than once, but I did get addicted to another much more powerful and dangerous drug for some time. A drug so powerful, my "stoner" friends thought I was insane for doing it, and kept trying to convince me to stop. Looking back, it was a real nightmare, and I have been very lucky.
I still experience some of the long-term effects, such as not knowing if an experience was real or a dream - I some times seriously wonder if certain occurences really happened or not. The temporary high you get from drugs is not worth the effects after it is over.
I experienced a lot of extreme anxiety and paranoia after I stopped using it - that sucks, especially when at one point you got over your social anxieties. It also caused me some depression, and even after I had decided to quit, I went back to it a few times.
Not to mention, once you become addicted, you will lose friends, and people will not want to be around you as much, and you will keep taking it to delude yourself that things are not so.
You'll do things you never would do while sober. You will lie, steal, break laws, betray friends and family, etc. all just to get your fix. When you look back on the experiences, you will be disgusted and you will not be able to imagine how it all happened. You will be a totally different person, and you will see a very dark side of yourself that you never imagined possible.
Then, every time I stopped, I would get paranoid. Being paranoid is really crazy because it is very real to you, while everyone else is convinced you're crazy. I still experience the paranoia effects, and have to convince myself that it's "in my head."
I never listened to people who told me not to do drugs. I thought they were a joke. I had so many close calls it's not funny. There are over 30 experiences that could have landed me on my death bed or in prison. I remember one time I was about to jump off a 4th story balcony because I thought I could fly, but luckily some guy held me back.
And these are just the psychological side-effects. What's really insane is that after all of this, part of my mind keeps urging me to do it again. WTF.
Perhaps you have to try it to really understand why they are so dangerous. But when you do get fvcked up, don't say no one warned you.