I think that only applies to other credit cards, but not debit cards or cash:

https://www.ftc.gov/tips-advice/business-center/guidance/new...

>Discounts to Customers A PCN cannot stop you from offering your customers a discount or another incentive for using a certain method of payment, as long as you offer it to all your customers and disclose the offer clearly and conspicuously. For example, you can offer your customers a discount or a coupon if they pay with cash or a debit card rather than a credit card.

Still, that kills any incentive for fee competition between cards - they all share the benefits of being convenient and face little pressure to change the fee structure.

But it’s not stopping the merchants from offering discounts for debit and cash, debit cards of which have capped fees and are very cheap to process.

Merchants are choosing not to give those customers discounts.