These are not financial transactions. The Mark is specifically said to be used to that "no man may buy or sell unless he have the Mark..."
...any sort of financial transaction,
If you must use a scanner for ALL financial transactions, then we are in big trouble.
Since this person was being required to use the scanner to get paid (a financial transaction), and it was scanning a part of his body, he had concerns and chose to take a stand for the sake of his soul. Exactly who are you to decide he is wrong in his belief? And do we want the government or even employers deciding which beliefs are valid? Because if we are going to allow that, you know that all beliefs against abortion and homosexuality will immediately be deemed invalid, and any objections to the same will be deemed illegal discrimination.
You use numbers for all financial transactions. Deposits, withdrawals, purchases, refunds, you name it. And you use scanners as well. A scanner reads the magnetic ink on deposit slips and checks. Items you purchase are scanned into the cash register. A scanner reads the strip on your credit card, as well as your debit card where you also enter a PIN number. Like I said, we're all doomed.