Because you can't drive after 1/2 pints? Not a lot of alcoholic drinks are actually nice enough to justify drinking "just because".
Walk? Get a taxi? Get a bus to town?
I don't drink "just because", I drink because I enjoy the social side of it, I work my way through 1 or 2 different bottles of ale or cider each week, it's a joy to try something different, sometimes its a disappointment, other times you find an absolute gem of a drink. I have a friend that brews his own beer, always pop round and have a couple when he bottles or barrels one of his new creations.