Adult men and women don't have time to smoke weed (or get drunk). They are busy and focused on working hard to contribute to society and to raise up their children and to attend to the business of active citizenship in democratic self government.
"It's called 'wasted' for a reason."
You are being sarcastic here right?
No. The emergence of effective birth control technology and social acceptance of abortion has caused many changes in human culture. Take those two changes away, and what you get are teenagers who have raging hormones but are told by a necessarily morally restrictive society that if they want to get laid, they must marry, and to marry, the man must have already established himself in the "world of men" so that the young woman knows that he is likely to be able to provide as she starts to pop out the children.
In such a scenario, by the time the young man is 25 years old, he has necessarily matured into a man who is capable of real love for a woman and capable of and determined to protect and provide for his dependants. The woman has also matured through the pain and hard work of child bearing and child care and the difficulties of managing a relationship with a man who suffers equal difficulties every day as he provides.
By the time you are in your 20's, that's what you are supposed to be like. That's the way that the biology works. Today, for a variety of reasons but with the primary cause being what I've said, we have males in their 20's, 30's, 40's and even 50's who have the emotional development level of a 13 year old.