re: Why do roofers never pickup the nails they leave behind?

Because they're fricking roofers. As a whole in a profession, they are the single worst group of people in America. It's what happens when you sit on a roof huffing in tar all day. They're basically retarded and really don't give a shite besides getting the most basic portions of a job done. Ask any contractor on who the worst people to deal with are, and I guarantee almost all of them say roofers with the occasional dry waller.