I'm not sure that underage drinking is an outlier, at least here in the US. In fact, the
majority of college students in the US violate drinking age laws.
https://www.niaaa.nih.gov/publications/brochures-and-fact-sh...
> If there were no drinking age laws kids would still not be drinking and smoking weed because parents wouldn't allow it.
In places with more relaxed drinking laws, we do often see more kids drinking. 42% of 15 year old boys were weekly drinkers in the UK in 2002.
https://www.euro.who.int/__data/assets/pdf_file/0007/382840/...
> Most young people begin using alcohol between the ages of 12 and 16, an age
at which they gain increasing independence and spend more time outside the home unsupervised. At the same time, the direct influence of parents diminishes and friends become increasingly
important.