I don't want mastercard supporting crypto. I want the merchants and payment providers supporting crypto so I do not have to use mastercard and their "rules". If I want to pay for porn or send a donation to wikileaks I do not want mastercard/paypal or anyone else other than the government (if it's legal I should be allowed to pay for it) deciding if that is ok.
Bitcoin transaction fees are currently around $8. My credit card pays me 2% to use it. No one wants to use the Bitcoin blockchain for average transactions. No one is buying Bitcoin as anything other than a speculative investment right now.
Also, your credit card pays you 2% because they extract a larger fee from the merchant, who will raise prices to cover that expense. So you're not really saving money.