You are only thinking this from the point of view of a software merchant, with low expenses. They can easily wait a few more months for the check to clear, but

You are only thinking this from the point of view of a software merchant, with low expenses. They can easily wait a few more months for the check to clear, but what if you are selling something that costs a significant portion of the sale price to make? Plenty of healthy businesses would either go bankrupt or have to delay shipment (which would royally piss off the customers, because from their point of view, they already paid...) if the money paid by customers suddenly took more than a week to arrive.