The same reason that Presidents, coaches, businessmen, and other people wear suits. It shows that you are a professional, respectable person. It is not a requirement in The Bible but an expectation of society.
Not all Baptist ushers wear white suits. This decision is made by the pastor of each church.
Clothes
Most ushers wear a suit and tie. There are usually no robes or vestments in the Baptist Church.
I do not believe there is any standard that ushers in Baptist churches wear gloves. I have not seen ushers wear gloves except in black churches.
It should be the bride that decides the color of the groom; best man; ushers and father's attire. If the groom, best man and ushers are wearing darker suits then the father should as well. No one should be in complete white other than the bride unless the bride decides she wants to be a little different. Although most whites seem white they are not and the bride should be the focal point and not the father.
White
suits white shirt red tie
For business, men should wear dark suits, white shirts and ties in the cities. In warmer areas, dress is less formal. Women should wear dresses and suits. Wear comfortable cotton in warmer areas.
People dress in their Sunday best to attend mariages. Men usually wear suits, Suits for men (even the groom), women wear smart dresses or tailleurs, the bride wear a white wedding dress.
mary mcleo bethune wore an ushers jaket with and white shirt under it and she wore a black skirt and also black flats
no they wear other color suits
in judo competitions on judoka wears white and one blue so the referee knows who's who.
because they want to look like retards in the movies