I've never had to wear a uniform, but in some instances, I think it makes people look very professional. When I hire a contractor to work at my house, I feel more sure of them when they've taken the time to have a clean uniform, or even just a shirt with the company logo on it. It shows they care about the company.
The only time I ever had to wear any kind of uniform was when I worked as a waitress and my parents had to get the clothes needed for me which was a white blouse, black knee-length skirt, tights and black shoes.
I do feel that is a uniform is required and mandatory, the company should either provide or at least offer help to get the uniform.