I honestly don't think it's actually an outlier issue. In highschool almost everyone I know got into smoking pot, at least for awhile, and within a year or two

I honestly don't think it's actually an outlier issue. In highschool almost everyone I know got into smoking pot, at least for awhile, and within a year or two 90+% of them just lost interest in it, maybe 5% kept using and maybe a quarter of them literally made pot the center of their lives and are still daily users with big impact on their lives and careers (or, honestly, lack thereof for all but one). The same thing happened with alcohol. As an adult, I've seen the same pattern repeat for people who just didn't try things, for whatever reason, or perhaps people who changed. What's actually happening, IMHO, is that you have a ton of overlapping processes that are filtering for with people who are vulnerable to becoming addicted to a given drug. Obviously those people will have trouble quitting.