> In the case of the debit card example (or credit cards) banks could do what they used to and actually decline the charge. However they've clearly figured out it's much more profitable to allow the charge and just hit people with (often excessive) overdraft and over credit limit fees.

It should be noted that overdraft services have been opt-in only since 2010:

https://www.consumerfinance.gov/rules-policy/regulations/100...