If you view human beings as perfectly rational machines then dress codes make no sense, but that's not what we are. Dressing formally puts you in a different frame of mind. It reminds you that your work is serious and that different standards apply to how you act and talk than in your casual personal life. If you dress to work the way you'd show up to a dive bar, then you're that much closer to behaving like you do a…
Actually, it makes me feel like I'm talking to a sales person. It is as if dressing up is used to conceal something about the intentions or shortcomings of the person. I probably don't explain it in the right way, but that is more or less the feeling it evokes.