Since I've worked in this industry from a couple sides, seen numbers around it and seen common retailer myths promulgated:
Checks are not free to accept. Lots of manual work to handle them, slows down the line, etc.
Cash is not free to accept. Slows down the line again. Mistakes happen when now throw everything into disarray. You need to count it at the end of shift, end of day, transport it or hire someone to transport it, etc.
Cards, are competitive in pricing per transaction, come out WAY ahead in the real world (on average, depends on business type) as they are faster so no one abandons lines, and they increase the number of items bought, and impulse buys.
There's a movement to require businesses to accept cash because of the unbanked and underbanked (mostly poor folks, and I am sure a few of you all) who have no bank account or high fees, limited access, so rely on cash. So you can expect cities and states to pass more must-accept-cash legislation.