They are a style. Halacha is only you have to wear a hat at certain (okay, almost all) times.
The goyim no longer wear fut hats. In America, they ceased being popular about 200 years ago. In Eastern Europe they lasted longer. Some cavalry were still wearing them up until the 20th century (when hats lost popularity among the military since they had to switch to metal helmets).
In America it has become a style among Jews. That gives it a halachic status, more so then when it was a sort of hat everyone wore. Similar things have happened to frock coats (our kapotes) and fedoras.
Like all clothing, they tend to “make a statement”. The only way to avoid making a statement with one’s clothes is to dress like everyone around you, and then you are making a statement that you are like everyone around you.