Unfortunately, dress codes and the tastes of the individual writing the codes, place the sanity of some codes in the mind and eye of the beholder. On the other hand, I can't think of anything so incongruous as the working population of Manhattan walking around in shorts. At any rate, where safety is not an issue, comfort should be the watchword. Again, I used to think that casual dress led to casual relationships and less productivity. The question of relationships remains, but the question of productivity is just the opposite of what I once believed.
Employees are more productive when they are comfortable.
No, I haven't proved it, but perhaps a company one day will put this to the test. However, in many companies it still denotes position. When I visit a dot-com, I have noticed that the president is usually dressed less casually than the troops. Sometimes, I have even seen a coat and tie, but I'll be that he has a meeting with a banker or backer. In time that too will change, probably sooner than all the other changes in dress that we've seen.