They are often in a situation where they can't or don't want to set the rod down. Most of these types of pics are taken by people that are wading or shore fishing. Most of the time I'll tuck the rod under my arm, but sometimes I need to be able to move both hands more than that allows, so ya, I hold the rod in my teeth. No pic involved.
bear i get this and i dont think anybody here can say they dont often find themselves
needing the 3rd hand. im guilty myself. if your chest deep thats 1 thing, but 99% of the time these folks are on boats and 2 feet next to shore.