So Europeans were sending 2 euro coins for recycling to China. The kind with two metals, white metal in the center surrounded by a yellow metal ring. To destroy them first, they just punched out the center inner white metal. Enterprising Chinese recyclers, instead of melting the metals, were putting them back together :)
There are people storing up closets full of the old full-copper pennies waiting for the day that the penny is discontinued and they can get scrap value that is higher than the face value. For now they aren't allowed to deface money so they're just storing them. I don't even know if it's worth the time spent sorting, but everyone needs a hobby.
Additionally, they're a real pain to melt down profitably, even if it were legal. It only makes sense at very large scale, which means only the companies that invest in big foundries will be making real money if it ever becomes legal to use copper pennies for copper.
A good analogy would be like collecting aluminum cans XD
It's illegal to do so, and the fines are very high.