This is just business and it has found the increase in the usage of bitcoin and other cryptocurrencies. For business growth it is always a must to move with the market trend and understanding the people's need. MasterCard is a billion dollar company, and it makes the largest number of transactions per second. If this has adopted cryptocurrency directly then it would've impacted the market big. What it has been doing is having third party services like bitpay that does the conversion of bitcoin and provides in fiat.

Mastercard doesn't have plans of receiving/accumulation of bitcoin. It has broadened it's business and not into real adoption.