Having cheerleaders at sporting events is as American as apple pie. Since high school, Americans have seen cheerleaders on so many sports games that they do not realize it's not the case elsewhere. In fact, many foreigners find the concept of cheerleaders quite strange.
A big part of that is that outside of America, different cultures think strangers to smile in public is bizarre. A foreign visitor may wonder why these scantily dressed ladies are so grinning? And why do we need these dances – is not the game enough entertainment?