The relationship is that the service and rewards you get are subsidised by generally poorer people who mess up their financial planning.
Rewards are paid out for transactions, not interest paid, that's all. Otherwise poor people failing payments would get more rewards than the rich which don't. The dynamics would be completely different.
Rewards are paid out for transactions, not interest paid, that's all. Otherwise poor people failing payments would get more rewards than the rich which don't. The dynamics would be completely different.