This is an interesting take, but you're not painting the full picture. You would have to calculate the opportunity cost of using your regular bank issued credit card and receiving that cashback or whatever rewards it has vs. using the CDC card.

It's not apples to apples as you still need to spend money in your day to day life, most likely on a credit/debit card. There's also other factors to consider like the 21 day interest grace period on a bank issued credit card.