Some of them don't dress like that. Modern Orthodox Jews tend to dress like the people around them (although with attention to modesty). However, Hasidic Jews frequently do dress in black and wear long coats. The reason lies in the belief that traditions are binding if they are followed by enough generations. The Hasidic community feels strongly bound by their traditions of clothing.Hats are a somewhat different issue: Jews have been wearing distinctive hats for at least 1600 years, and in most branches of Judaism, it is considered improper to pray bare-headed. If you keep the commandments scrupulously, you have to say little blessings hundreds of times a day, so having a hat on at all times makes good sense. This can range from a yarmulke or kippah (a beany) to a regular straw hat or fedo