Of course, many people go just to get drunk. We have about 6,7 million visitors every year and they drink loooots of beer. I think this year we had a total of 7 million beers sold. You can imagine what that means in party and else :D

But yes, at least Munich /German people all come dressed up in traditional close. You will see it a lot when you go there. - Its even almost a must (at least for us), that's why many tourists try to imitate it. They don't want to stand out of the rest :D