I've seen this news creep up every now and then. Never seen any actual announcement nor seen it in practice.
microsoft's acceptance of bitcoin is super limited and always has been. you can't actually use it for purchases in the microsoft online store---only for "games, movies, and apps in the Windows and Xbox stores". source: https://support.microsoft.com/en-us/help/13942/microsoft-account-how-to-use-bitcoin-to-add-money-to-your-account
so you can't even buy windows with it.
I think it must be very difficult for a public company to demonstrate that a payment method is also an investment. And that this investment is highly volatile.
if volume is low enough (ie amazon can't really do this), they can just use payment processors and avoid volatility altogether. at the rates coinpayments or bitpay charges, it's cheaper than credit cards. but there needs to be enough demand from consumers for merchants to justify the time and costs of integrating it.