With JSON blobs in simple tables a very large part of designing a database schema becomes designing a JSON schema, with different opportunities to make mistakes but (potentially) the same strictness.
define schema with data class and you have tools like protobuf/thrift. And I find it really unnecessary to map every attribute to a SQL column.
We are talking about the internal database of some application: its schema is something that should be designed well, not enforced defensively like a schema for validating undependable inputs.