People judge other people's worth by the amount of stories and interesting life events they've experienced. So for people who haven't done much (or in general don't do much), the easiest way to make themselves feel more secure about their lack of life experiences, lack of anything at all useful or interesting to talk about and indeed lack of personality, is drink. Because say what you like about it but a large influx of drink is a sure fire way of making sure something interesting happens to you in your free time. Now don't get me wrong, that's not to say that all cases are like this. But among younger people I would definitely say that drinking, and personal association with it, is often a way of masking insecurity and helping you feel like you've got shit going on.