CouchDB is a fantastic database, but setting it up for local development is not easy, as it also requires an Erlang runtime environment. Having a built-in PouchDB-Server in our apps will make CouchDB optional. Many Apps require couchdb users / admins / security settings etc. Using PouchDB makes it simple to isolate these in local development. (But if you don't mind the CouchDB dependency, you can also use node-multicouch for that).