That’s a common argument in favor of the dress code, but I think just as many companies just require the same for everyone across the board.
I worked at one company, a plumbing supply wholesaler, where the principle was pretty much turned on its head. Those who worked at the retail outlets wore pretty much anything they pleased other than open toed sandals or shorts, for safety reasons. The culture of the corporate back office was much more formal. They never actually came out and said the rank-and-file had to wear ties, but the managers did. And they banned jeans after I had been there several years. It seems like if the article your company deals in is blue-collar in its nature, the back office honchos tend to want their staff to dress up more, to distinguish themselves from the people who actually handle and sell the stock.
Suits and jacket-and-tie combos used to be the mark of the upper class, but in the L.A. area that’s pretty much turned on its head as well. The streets of Beverly Hills on any Saturday are full of well-heeled, denim clad shoppers who have just left stores staffed by low paid, suit wearing workers. The tellers at the bank are almost invariably more formally dressed than the customers queing up to do business with them. I understand why some people advocate a professional, businesslike appearance. It’s also useful for customers to be able to identify at a glance the people who work in a store. But sometimes requiring public contact employees to dress up as if they’re in Sunday school seems unfair. There are other ways store staff can be made to stand out … it’s a tough job they have; why make it harder?