What?! That's nutty.
I can see maybe debating whether it's OK to pay inside but I can't fathom how it's any safer to have a crawling baby in one arm, hold a toddlers hand with the other and somehow keep everyone from darting in front of cars or licking things while you pump gas vs keeping them in their seats while you make silly faces through the car windows and slide a card through the pump reader. What did parents do before pay at the pump? What's the real risk level of being 30 feet from your child for a minute or two?