It is all fun and games "defending" legalization of weed online until you get a substance abuser in your family.
I guess what I mean is, nicotine is more self-contained than the others.
The problem is that it's a slow burn because it's consumed by smoking, and this is really the most pleasant way to consume it. People don't like the externalities associated with it, and that's pretty much it.
Perhaps the reason you don't see that is it is more difficult for teenagers to get alcohol. At one point in my life it was actually more difficult for teenagers to get alcohol than it was for them to get marijuana