Invented? That seems a bit of a bold claim. Surely someone just said “hey, why don’t we just put some sticky backed plastic on it”.
It’s not ‘sticky backed plastic’ like you’d put on your school books, it’s polyurethane, which is more like rubber.
So when you (or a rock) hits it, it absorbs the energy and bounces it off.
As crashtestmonkey said, they apply it to the front of helicopter blades to protect from all the sand/dust/gravel/rocks that get kicked up. Then boy racers discovered it was great for protecting the fronts of lowered cars, then mountainbikers caught on.
Having written that defense, I put some on a frame, it made the frame look like crap for the time I owned it, peeled it off and the next owner got a new looking frame. Seemed a waste of owning a nice shiny new frame!
I now just make sure the cables are run properly and don’t rub!