All of those are blob/file based, when the service provider needs to offer services like search and ways to make deeper inferences between pieces of data it's pretty much impossible to have all the encryption handled client-side.

I'd be interested to see examples/arguments where it works though.

This is an extreme use case. For example, S3 is HIPAA compliant, so I'm sure there's plenty of very private medical data that's not encrypted on S3.