I remember a consultant giving a lecture about consulting and he said one of the things that become important is to dress to meet expectations.

If you're a creative consultant, dress creatively. If you're a business consultant, dress for business.

It's part of his act, he dresses casually to signal that he doesn't care about the traditional way of doing things. He dresses poorly because people expect it of the tech nerd.

He's dressed up in court because he's not stupid and isn't going to piss off the court.