Since paypal is basically ebay owned and not accepted at amazon it does make sense they might incorporate a crypto as a way to attack paypal. Maybe they will launch amazon coin we will see.
Paypal and Ebay are two separate companies for a long time now. Amazon has never included Paypal because Amazon considers Paypal as a competitor directly and not directly. If you use Amazon you have noticed this company is not accepting any payment processor. They accept only Visa/Mastercard, gift cards, etc.
They have already Amazon Payment that they struggle to be adopted so I don't think they are ready to create their coin anytime soon.
If amazon will start its own coin that will not be so successful because people already have a emerging coin that gives a lot to the people and thats the main reason bitcoin is accepted by the amazon and this will give amazon extension for surviving in the upcoming era and more to it this is an ease to the bitcoin use that they can shop from amazon without any worry and in future many other stores will accept btc.