From my point of view, companies with sizes like the above mentioned (refering to cash flows and generated income) are normally risk averse and therefore it seems counter intuitive to me to accept BTC as a payment method due to its heavy volatility.
Moreover, not knowing how regulation might influence the outcome for BTC is another argument for not accepting it?!
Well, crypto currency is very new. So Big corporation have to "touch" this potential market. Before this market is occupied, they have to do something to "control" it. They don't care how the bitcoin price is. They just want to be part of this lucrative market. Microsoft is tech corp, Paypal is online payment corp. Blockchain technology's is the thing they need.