While I agree it's not hard to make an object safe for concurrency, knowing how to do it effectively is another matter. In an organization or team where there are engineers at all levels of familiarity with java, getting concurrency right is a PITA.

Additionally in this context, the very basis of the channel mechanism is "share state by communicating, don't communicate by sharing state". Also pass by value lends itself well to remoting if I choose to go in that direction.