I once sat a desk next to another developer. He finished a UI control in 3 days, and then found out it completely replaced a legacy control that took multiple

I once sat a desk next to another developer. He finished a UI control in 3 days, and then found out it completely replaced a legacy control that took multiple developers six months to finish. And then shortly thereafter we both got laid off, and the slower folks kept their jobs. It is a mistake to believe that the only requirements are the ones that the developers get to see.