I agree. The way I see it, a document DB (I have used Firebase) has features that make it nicer to work with documents. For example Firebase let's you query and index based on the data within the "JSON" (in quotes because it is not really represented in Firebase as JSON, but is close in structure).

Another thing is you might want the lack of features. I.e. you want it so people don't do joins etc. Because you want the team to use the same paradigm with local data as with server hosted. I can think of reasons why.