In New Zealand, most low margin business (like cafes) ask you to accept an ~2.5% transaction fee (if you use a credit card or paywave). You can avoid the fee by using a debit card with a chip.

I'm unsure what choice the poorer make. If you're actually low income, maybe you don't go to cafes.

I did notice that a thrift store didn't charge the extra 2.5%: so perhaps poorer people have more pressure to use cards with fees?

Amex is noted for its high fees - so perhaps it is a bathtub where only the middleclass care.