> However, there was nothing stoping Rethink from building their own service and promoting it as the "official" RethinkDB service.

Nothing except the facts that writing a database engine and doing DBaaS are two entirely different things to get right, it would have required at least double the money and headcount, it would have caused even more risk on the consumer side, and ultimately diluted RethinkDB's core competency. Other than that, great idea.