They all deploy web apps at the edge, so are distributed by default. A lot of the web apps deployed on these services have small volumes of data, read heavy and low writes. They are also low system resources so an embedded db makes sense?
Running SQLLite locally to the application will give extremely low read latency with most of the apps being read heavy/biased. The sales pitch for deploying at the edge is you can have hundreds of apps running across the globe near your users transparently.
I’m fairly interested in LiteFS as a distributed cache. I’ve seen systems use a message queue listening for updates then updating local caches which is a bunch of custom code/plumbing that can be replaced with LiteFS. Using LiteFS the read replicas are essentially materialised views.