flying j and receipts

If I had to guess, it would be the same reason Walmart puts the milk at the back of the store instead of right at the registers. It makes you walk past merchandise you might decide to pick up. Impulse buys are money in their pockets. Add to that the risk of an employee walking to the pumps to replace the paper receipt roll. One workman's comp claim for somebody getting hit while out there reduces profits and increases insurance rates for the business.
Not justifying it either way. Just guessing why they would do it.