Once you involve the law after finding a pattern of wrongdoing they get a small fine and move on to the next scam.
> 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.
I've successfully gotten the law involved with Citibank with a time investment of around 10, maybe 15 minutes. All I did was filled out this form: https://www.consumerfinance.gov/complaint/ and they handled it from there. However, the CFBP has only been around for less than a decade.