Imagine lots of shops issuing these tokens, the public will start using them because they get discounts and benefits for holding them
Maybe I am getting sidetracked, but could it happen that some less morally inclined personnel might embezzle a portion of those tokens that are as you say obviously valuable?
I guess there will be an restriction so that these merchant tokens only get transferable to a user's GAT wallet when there is actually some kind of proof of purchase/payment at the checkout. Otherwise the cashier could send himself some tokens to his wallet.