That's one big reason, but the other is numbing bad feelings, which I think is a more interesting field, especially since it often blurs into the social bit.

Indeed, for the social aspect, everyone is already fully aware it's not needed, and that they can have fun socialization without it, because of their childhoods.

I think the biggest reason alcohol is used is, to put it bluntly, how painful life is.

As the child grows into an adult, and realizes the real nature of life and the world, baseline pain increases. And it's hard to be social when you're worried about things or down about things.

But alcohol is a cheap, readily available blunt instrument against this pain. No matter how bad you feel, if you down a litre of booze, that pain will definitely, and quickly, stop.