Life isn’t getting any slower. This means that because people have jobs and families and friends and obligations, for many of them shopping is not something that they look forward to doing. It’s a have-to, so the business with the best merchant services is going to be the one where they shop.
They want to get in, find what they need, and get out.
And counting cash takes up time in the line. Counting the customer’s cash at least twice, and then counting out the change at least twice means a few extra moments per customer. Checks take time, as it has to be written, and identification must be examined, phone number written down, etc.
Compare that with the speed of the credit card. Zip, sign, and out.