Had an eye exam this morning and I needed to do a $30 co-pay. Pulled out a card to pay and I was asked if it was a credit card. I said yes and she said there

Had an eye exam this morning and I needed to do a $30 co-pay. Pulled out a card to pay and I was asked if it was a credit card. I said yes and she said there'd be a 3% fee for using a credit card. I switched to my Discover debit card, which pays 1% back. My only recent experiences with this with transactions over $10 was a small restaurant and a construction project where they took the deposit on a card but would charge a 3% fee if we didn't pay by check. Many of the local convenience stores charge a fee to use a card.