That's not the way it works. The card issuer charges the merchant a fee on every transaction, usually consisting of a small fixed transaction fee, and then a percentage of the total amount. If you buy something for $10 on your Mastercard, the merchant may only get $9.50. (Or whatever, there are lots of credit processors and aggregation programs, etc.) That's why so many places have a minimum purchase amount for credit card transactions. The credit card companies aren't so stupid as to set up a program where they lose money when you use your card. Hell, they probably have a way to make money even when you don't pay the bill!
I hear what you're saying from the merchants interactions with the banks. Me as the consumer, waiting even a day and up to almost a month (if ya time the purchases)before paying your bill is money they don't have. Lending institutions make mucho bucks on the floats. Between losing interest charges, processing of purchases, statements, card "compromise"( the euphemism they use for stolen card or identity)
and daily float loses, it
cost the bank money when you have no month to month balance. hence their "deadbeat" description
Just an aside, and something I've recently learned from a friend, if you run up big credit card debt, and pay the minimum amount on time, the banks and credit reports have you as a person with good credit. That's why he keeps getting card offers which only makes his finances worse.