Choices: Not much choice but the fit is important
Uniformed employees can either look polished or like they're wearing someone else's clothes, which I suppose they are. The idea of wearing a "monkey suit", a derogatory name my generation used for the uniform, was not in keeping with the notion of individuality. However, whether a work situation or a sport event, uniforms identify the wearer to the world and so the world knows what one is representing or for what one is responsible.
Flight attendants have the look of "business smart", which is necessary for their position. With the exception of police officers and other "power" uniforms, not all uniformed employees look polished and smart. Short of "scrubs" in a hospital or "overalls", uniforms need to fit. And the reason uniformed employees may not look so put together is more often because of the fit of the uniform than the uniform itself.
On my recent trip to Europe, an Air Canada employee at Pierre Elliot Trudeau airport in Montreal looked as if her pants were three sizes too big for her. They were cinched at the waist and her vest covered the bulging excess fabric. It appeared as if she had lost a lot of weight but hadn't had time to get a new uniform; although the vest did fit her well. Obviously there were no trousers in the cache that fit her.
Servers in restaurants will often wear black and white which should look good on everyone. Here we go again - it is the fit that counts and not necessarily the "uniform" itself. If you are wearing your own clothes, of course, they should fit properly. Restaurants will often allow "individuality" in jewellery; however even that may be mandated. Some chain restaurants will tell servers and hosts/hostesses how they must accessorize - some say they may wear silver jewellery but not gold, or gold jewellery but not silver. It is to be uniform after all.
There was a time when health care professionals had to wear a specific uniform. Now, particularly in places such as personal care homes and "old age" homes, employees are encouraged to wear "regular" clothing to make the residents feel "at home". It is true, I suppose, but visitors and residents themselves may become confused. When visiting my mother one time, a resident asked me to do something. I responded by telling her that I was not an employee, that I was visiting my mother. Well . . . the commotion that set about at that time was embarrassing for all concerned. In the big picture though, I am sure it is a better idea than having starched whites.
I have never had to wear a uniform; although one might argue that the "business suit" is a uniform of sorts. All I can conclude is: make sure the "monkey suit" fits!