Why do certain gas stations add a surcharge for credit card payments?

Gas stations make really low margins when selling gasoline. For them to dish out acquiring fees from this already low margin, would not be financially beneficial for them. This is why in most countries around the world, when you use your credit card for purchase of gasoline, you can be charged on-top.

The practice depends gas-station to gas-station. This decision solely lies with the Oil company that they are marketing/selling.