Your comment is spot on. e2ee is critical when there is server side replication or when you are using a public server, but neither is typically the case with Databag. e2ee imposes some limitations such as preventing server side processing of content which is useful for streaming. In my opinion e2ee is needed when you don't know where the content resides, but when you do it's overkill.
with databag, the content only resides on the hosting node, or on the device of a topic participant. in the case of matrix.org, federation means your content will live on other servers, but that's not the case for databag.
your point about the admin being able to see the content is valid. if the databag node is hosted by someone else, then they to would have access to the content if e2ee is not used.