Seriously? Really? I saw KISS a few years ago, and I can't even remember the slightest bit of pot smoke. Half the crowd was over 40 years old, and there were tons of early teens.
I still go to a LOT of concerts, especially classic rock ones, and this isn't the 70's or 80's.... very little pot smoking goes on at these things compared to the old days.
BTW, I do remember the 2 concerts I attended where pot smoking was the absolute worst.... ZZ Top, and the Marshall Tucker Band. I'm pretty sure I was fully stoned by the time I left MTB, and I didn't smoke anything!