Everyone is missing the main point of this partnership..
By merging data about every purchase, both Amazon and stripe benefit dramatically from lowered fraud rates.
Suddenly Amazon now knows when payments on your card are likely to bounce because you're at your credit limit, so they can pick the best time to send you promotional messages.
Stripe 'intelligence' can now have a much stronger good/bad signal for every card.
This deal is primarily a data deal, and both parties will benefit to the tune of hundreds of millions of dollars.