Underaged Drinking

So I have recently noticed that Harry Potter and his friends seem to be drinking heavily every time they visit Hogsmeade, and no one cares. At all. In fact, it doesn't seem to be illegal, or even frowned upon. WHAT is up with that? Well, their drink of choice is called butterbeer. I have never actually encountered this drink, so I'm not sure that it's real, and none of the books actually say whether or not it contains alcohol (or whatever substance wizards prefer to intoxicate themselves with), but from what I gather, it appears to contain an equivalent amount of whatever substance to the level of alcohol in beer. While I personally would not want to make it any easier for supernaturally powerful, hormonal teenagers to get drunk and impair whatever judgement they had, the wizarding world seems perfectly okay with it, so I suppose that's that.