In volleyball, back and forth volleys make for an exciting match. It takes more power to get a kill or instantaneous point, but it is thrilling (for the audience at least) when the ball is hit back and forth over the net.
Email is not like volleyball. If you find yourself in an email exchange that has volleyed back and forth more than a time or two, it's time to pick up the phone or have a face to face conversation with the parties involved.
The volleyball player does not have a choice as to whether or not to keep returning the ball over the net. With email volleys, you do.