Then it becomes plain that the credit card company has something to hide.
The whole point of regulatory capture (from the perspective of the regulated industry) is that favorable rules are generated, and the industry may still protest publicallypublicly how they chafe under the regulations.

Why can’t the credit card issuers simply ban surcharges as a matter of contract?

I found this with a quick Internet search:

“Pursuant to a settlement of the U.S. merchant class litigation, Mastercard will modify certain rules and business practices to permit U.S. merchants to apply an extra checkout fee, also known as a surcharge, to customers who pay with Mastercard-branded credit cards. The rule change permitting such surcharging will go into effect on January 27, 2013.”

So it looks like they can’t because of a lawsuit settlement.