The number of outlets where alcohol can be purchased must have quadrupled over the last 20 years. That in itself bring extra competition, and prices much cheaper relatively.
Another factor, is what we buy. 20 years ago, it would have been bitter or lager at about 3.5 - 4%. Now it is more likely to be Ciders, lagers or alcho-pops at 5%+. Girls have been heavily marketed at, and they are just as likely to get smashed than the lads.
Added to all that, the demise of the local pub. Here, the landlord kept an eye on his customers, and refused (enforced by law) to serve people who were too drunk. He could lose his license (and livelihood) if people were found to be intoxicated on his premises, so they self police rigurously.
The average young person today starts off at home on cheap booze from the supermarkets, and they are already drunk when they go into the clubs where it is impossible to keep tabs on the hundreds of drinkers. The result is many get very very drunk.
Unfortunately, all the answers seem to penalise sensible drinkers as much as the problem ones.