True, but you take money out of an ATM and it is certainly possible that the records are retainied. If all cash registers used the scanners it would be trivial to track individual bills.
I haven't used an ATM in nearly 10 years...........
Plus, only the larger bills need to be verified, $20,$50,$100. They are the ones most counterfeiters cherish. And also, the transactions themselves need not be kept track of only the bill being used at place date and time. If the same s/n is used 2 minutes later 10 miles away, then BINGO! you have a winner!............