Copyrighting Football Plays

I would never have even considered the question, "Why aren't innovative football plays protected against copying?" unless I'd read this Freakonomics article on that very topic. Also, I'm guessing that anyone who's not a diehard football fan will probably be as surprised as I was to learn that the forward pass has only been allowed in the game for a little over a century now (or that its inclusion came about after a rash of injuries and deaths resulted in the U.S. President demanding changes). Hard to imagine there was a time when every play was a run, but prior to 1905, that was football for you. Weird!