Presumably this is to pay for all the points people get by using cards, not to mention the sign up promotions.

I like how in Europe and Australia interchange fees are capped. Even if it means they live without such bountiful premium cards.

https://en.wikipedia.org/wiki/Interchange_fee >> In the United States, the fee averages approximately 2% of transaction value.[2] In the EU, interchange fees are capped to 0.3% of the transaction for credit cards and to 0.2% for debit cards.[3]