According to American law and Visa and MasterCard policies, cash discounts are allowed. The use of a cash discount is becoming more widespread. Businesses display signs stating that a service fee, such as 4%, will be applied to all stated prices, but that customers who pay with cash won't be charged the cost. In other words, everything other than cash will be subject to the fee: purchases made using credit cards, debit cards, and prepaid cards.
The service charge can significantly reduce the costs associated with accepting card payments, saving businesses money. Cash discount offer the advantage of mitigating the expenses of debit card payments while surcharge programs are restricted by law to credit cards. Naturally, they encourage more clients to pay with cash as well. This, in my opinion, explains the current enthusiasm for cash discount.