I'm all-in on AWS and I've drank the kool-aid so I'm obviously biased but I've quite enjoyed living in the AWS walled garden. Stripe is one of 1-2 external services I use, bringing that "in house" would be nice, especially if CDK had full support for creating merchants/etc.
[0] https://archive.is/R7m9s / https://www.allthingsdistributed.com/2007/08/the_amazon_flex...
Except for this, it's great.
It would be a large acquisition but not unheard of.
It was very ambitious, supporting a scripting language for what are now called smart contracts, and very complex payment schemes.
It was also a huge pain in the ass to integrate, and the user payment flow was wonky, with a redirect to multiple amazon branded pages to log in to amazon, then redirect back to finish the transaction.
I've not used stripe, but people who have tell me it is super easy to integrate.
If Amazon has indeed done an evaluation that Strip is more cost-efficient, secure, flexible, or whatever, than maintaining their own payment processing, they don't want to be in a position of Stripe strong-arming them down the road.