I have noticed gas stations are more prone to this (along with very small business), although it happens on occasion at restaurants as well. I figure, with 3% restaurant rewards, I break even at 3% restaurant charge and or using cash.
Why would businesses that offers a cash discount (which means they also accept credit/debit) lose customers?
Ie; gas station 1 has a 3c cash discount. Gas station 2 has no discount, but you don't feel like you're not getting the discount. Gas station 3 can even compete by having a 1c credit discount.
The dominance of cards is mostly American or, at the very least, location-dependent.