I think there's just a statistically reliable number of people who will carry X balance at Y interest rate, and card companies use perks as product differentiat

I think there's just a statistically reliable number of people who will carry X balance at Y interest rate, and card companies use perks as product differentiation so they can attract more users. If the perks somehow get even more people to ignore their balances, that's just a bonus. At the end of the day the card companies are competing against each other.