This one doesn't need money ;) I would suspect other things being equal, hanging about with little to do would that costs money would encourage socialisation and sex.
Anecdotally, I feel kids are more mature in many ways than my generation (I'm late 30's). They have total access to information and I suspect this helps them learn to see the world faster.
As for less drinking/drugs, I wonder if smartphones have a big impact. In my youth we'd underage drink with friends and get a bit loose. Now days that behaviour would get uploaded fast and probably stop us doing it.