I got really confused by ARCO because for ages the only one I went to was at SMF. So I got pretty indignant when the next ARCO I went to that wasn't at SMF had an attendant that insisted none of them took credit cards.
Anyway, I think that the SMF one is required to take credit cards by the airport authority (which I think owns the land the station is on). Could you imagine being the gas station all the business travelers went through and have them NOT take credit cards? The place wouldn't be open 24 hours before a riot would burn the fucker down!