Note I said "AWS primitives", not AWS as a primitive. I think they're overly expensive unless you're using them for prototyping, as you should eventually move off to your own gear once you know what your load/compute/storage profiles look like.
I appreciate you pointing out that this is most valuable when you're _not_ running in AWS (I work at a startup that wants to use this tech in AWS, hence my not understanding why we'd waste additional abstraction for little additional benefit).
Disclaimer: I _want_ to move off of AWS to our own physical gear at some point, but our dev team is married to it because they're afraid of physical infrastructure (but its okay when critical services like EC2, autoscaling, and IAM aren't working for several hours apparently).