If they even bother investigating. From the sibling comment:

> But who's going to investigate Wells Fargo over a $15 "mistake" that they fix as soon as you ask them to?

The bureaucracy to file charges for something so small is a non-starter. It's probably happening to tens of thousands of other customers, but then you have to do the leg-work to get other people on board. There's nothing you can do involving the law that doesn't require a significant time investment. And as you've said, the punishment is such a pittance that all the hard work didn't matter in the end.