Why are restaurants charging a processing fee?

Why exactly are restaurants resorting to charging a processing fee? It seems like an unusual practice that is catching on in recent times. Could it be that the cost of doing business, especially with regards to accepting credit and debit card payments, has significantly risen? Or is it a way for restaurants to offset the fees they are charged by third-party payment processors? It's intriguing to understand the motivation behind this trend and how it ultimately impacts both the restaurant owners and their customers.