Why are a lot of teens today hooked on heroin?

I was in the grocery today and I heard two women talking about their teenage daughters, both of which are addicted to heroin. I heard them talk about treatments, and how they’re going to get their daughters to change their ways. As I heard this, I just can’t help but wonder why these teens are wasting their youth taking drugs. I have a teenage daughter myself, and I don’t want her to take heroin.