Maybe my memory is faulty, but I never remembered having to pay a surcharge to use a credit card. Now everywhere I go there are signs saying that there is a 2.5-3.5% surcharge to use a car (and others that say that there’s a 2.5-3.5% discount for using cash, I assume to get around wording)
I’ve been in the POS business for 25 years, and deal with the credit card side a lot.
A very large part of this is POS companies often have a relationship with the credit card processor (or are owned by a processor), and make a lot of money from the processing fees. The higher the fee on the processing account, the more they make.
So they convince the merchant (restaurant or store) that they can have a free system by passing the cost to the customer. Often times they are just waiving the monthly subscription fee, but some will also give the merchant free hardware as well (with a multi year contract).
Then they jack up the fees on the processing side: Since the merchant no longer has to pay the 2.5% - 3% fee that they were paying before, they allow the credit card / POS company to charge them 3% - 4%, and then pass it to the customer.