Exactly.
And sure, you can use S3/Dynamo/Aurora from an EC2 box, but what would be the point of that? Just get the app running in a container, and we can look into infrastructure later.
It's a very common refrain. That's why I believe Docker is strongly to linked the development of these proprietary, cloud based models of computing, that place containerisation at the heart of an ecosystem that bastardises the classic idea of a 'server'.
The existence of S3 is one good result of this. IAM, on the other hand, can die in dumpster fire. Though it won't...