The sword cuts both ways
There are those on both sides of this issue that are obsessing over appearances and attempting to use appearance to imply competence. The range extends from barefoot boy, who appears to believe you can't possibly be right if you wear shoes, to you, who seems to believe that anything less than suit and tie is sloppy dress and therefore sloppy job performance.
A dress code, if required, should be situational. I really don't see why a backroom coder who never sees the customer should be required to wear anything more than necessary to avoid violating indecent exposure laws. An on-site salesman, on the other hand, should be appropriately dressed for the customer's environment. That may mean suit and tie, that may mean jeans and a tie, that may even mean shorts and a t-shirt.
Me wearing a tie to work is not going to happen. My job can require that I climb into the ceiling, crawl into a checkstand, lie down on my back to remove mounted equipment or on my stomach to reach behind it. Long pants and closed-toe shoes are required for safety. I go to work dressed in pants or slacks, a collared shirt (usually a polo, occasionally a button-down), and shoes. Every day. After-hours page-outs are "come-as-you-are", so I get to wear jeans, t-shirts, and sneakers.
A tie is a safety hazard. I might leave home wearing one, but I'll remove it before I go inside at my first call. Might as well leave home without it.
