Engen please respond!!

Hi i have filled up at engen garages many times & found out that ebucks card can be swiped .

However i have been told that a person only qualifies if paying by cash,debit or credit card AND NOT if a person has an account with the garage to fill up.

Can anyone please give me a logical & justified reply to this as i find it totally unacceptable and demotivated to even fill up at Engen again.

Card,cash or account, the system should be designed to use ones ebucks card.!!!