There's a story behind that picture in which Joe says he lost his original cap in a carpark tussle with this guy Corn pop. Corn pop was a bad dude. He recovered it from Corn Pop by threatening him with a length of chain and just to troll Corn Pop he wore that hat from then on wherever he would go.
'A bad dude who ran a bunch of bad boys. A razor-armed gang leader in Wilmington, Delaware, who was confronted and stared down by then-lifeguard Joe Biden and a six-foot chain. CornPop thought he ran the swimming pool, but he was vanquished by Joe Biden.' Hahaha