Nowadays a lot of people like to fashion themselves in a way that is less traditional. You might see men wear make up or men and women coloring their hair some color that isn't naturally possible. Since society is so free, even among serious scholars (as I see in my department), what is the point of having a strict dress code?
I imagine one doesn't want someone showing up scantily clad or maybe there is a uniform requirement to represent a certain party or for a certain type of job but there doesn't seem to be much point for specifying such at social events in places such as conferences.
Maybe if you turned up looking like a tramp. People might think you had slipped by the security or reception, and shouldnt be there.
Uniforms take the decision making out dressing. If you are a member of a team and you all rack up to work wearing the same team tee shirt, you will all be recognized as part of the team. ie business people etc, often rack up to work in shirt and tie.
In some failing schools teachers have appeared to dress like the students, and be friendly. The children lose respect for the teachers. In good schools the teachers normally dress smartly.
The police wear uniforms, this lends them a little protection in their work, over a person dressed as a tramp trying to stop a robbery.
Uniforms seem to engender respect in most people, except perhaps teenagers who might want to rebel against authority, and maybe also junior lecturers with pink or green hair etc that perhaps still think they are teenagers, and will not conform.
If you dress scruffily and try and sell a product, are you as likely to sell it as some one dressed smartly.