I was a teen in the late 90s, and was friends with a lot of the druggie/stoner/party crowd. By and large, these people do not have kids, because they can't afford to. A good many of them are dead now, either from overdoses, or drug-related accidents (like crashing their car while going 100 mph while high), or suicide.
The 55 years of American history post-WW2 was a bubble, where people could get away with a number of not-very-adaptive behaviors because the whole country was on top of the world. The last 20 years has rapidly exposed this as a bubble, and the folks who were swimming naked when the tide ran out didn't leave offspring to be part of the next generation.