A few years ago a law was passed in the US making it illegal to melt down pennies and nickles. There is also a law against taking more than $5 worth of pennies out of the US. People still hoard copper pennies on the hope that the US will do away with pennies and they will be able to melt them.
...and others just melt them anyway, because they know the law can't be enforced, especially in small operations involving a few people.
Refining to purity is what requires a larger operation. If you just melt the coins into bars or cubes, it's not 99.9% copper, so you have to ship the bars to the refinery to make them 99.9... if you do that, then you are using two heat cycles one for initial melt and one for refining (=more energy expended) so in that regard there is a loss. But it's still cheaper than moving them to Canada for melting (as they used to).