Drug mules are

not rare - and yes, some people do it unwittingly. 
There was a case some years ago, in France I think, where someone was caught bringing drugs into the country. His or her reaction on being found apparently made it very obvious they had no idea the drugs were there. 
That individual was fortunate. If the country had been one like Indonesia then it is unlikely they would have had much sympathy.
It is one of the things which worries me about travelling - and having members of my family travel. I am always concerned that someone else will try to use them as unwitting mules.
It's a topic of media interest right now. There are claims that the "innocent" young woman who was caught in Colombia was actually a sex worker and that the safety of her family was threatened if she did not attempt to smuggle the drugs. I don't know whether there is any truth in the claims. The media loves to sensationalise such things and the state newspaper is, at times, rather like the old "News of the World".
Through the school system I know someone who lost a son through drug dealing. He was murdered in a remote location over a drug deal which went wrong. Nobody talked about it much then and nobody talks about it now. Now it is as if the matter never occurred. Nobody mentions M's son to her. I often wonder what she thinks, what she remembers on his birthday and the date of his death. It must be hard. He was, when I knew the family, a happy enough kid who liked kicking a football around but never worked hard enough to be on the team. He wasn't terribly interested in school but he was always happy to help someone. He would wander into the library at lunch time, look in the waste paper basket and, if it had anything in it, he would empty it without being asked. As I didn't have a "bin monitor" in the library I appreciated that - even if he never opened a book if he could avoid it.
And then there is the other mother I know whose daughter works in the "sex industry". She is, quite simply, a high class prostitute. Her life appears to be one long round of lunches, dinners, parties,  holidays and more. It isn't of course. She "pays" for all that. It worries her mother sick. Her daughter "got in with the wrong crowd" and uses drugs as well. 
      "I know what will happen," her mother told me the other day, "She'll take a b..... overdose or end up like that creature in the paper."
Maybe. Maybe not. Whatever happens it won't be a happy outcome. Her daughter never opened a book if she could avoid it. She has no apparent hobbies or interests. 
Perhaps that is all part of the problem. Nobody in my immediate family smokes. The idea of "doing drugs" has never remotely interested them. They have other interests.
The Senior Cat has far too much timber. My mother had far too many sewing materials. I have too much yarn. My brother has too many computer components (he builds them for the fun of it), Middle Cat has too many painting materials and the youngest of us has too many craft materials. The next generation is no better.
I suppose all this is a substitute for the evils of drugs. I feel sorry for people who need drugs. Playing with yarn is much more fun.