For many, the substance one is addicted to generally starts out as something seen as fun and enjoyable. Take alcohol, the most widely celebrated addictive toxin in the world.
Stick with it for a bit, integrate into your life as a crutch (bad social skills, try drinking! need a way to relax, try drinking! bored, try drinking!) and eventually the effects of withdrawal keep you hooked. Even if you think you're not hooked, there's a chance you are.
It's a slide that is very difficult to travel in the opposite direction on. Some people will certainly slide further down due to life circumstances, but that's not really the problem, is it? You can't eliminate the fact that life is eventually going to really suck at one time or another.
The problem is that we allow companies to profit from addictive and usually harmful substances, and they are incentivized to keep people addicted. Alcohol, tobacco, and opiates - the root of an astounding amount of poor health, financial struggle, and early death among otherwise ordinary people.
Addiction isn't a moral failing of the individual as much as it is one of society, but in my opinion, for different reasons.
Think about it, there's real truth to it.