You really are missing the point. The black box and any associated transmitting beacons which can give away its' position are designed to be found with the bulk of the wreckage. If the black box had ejected, as you so wished, then it could have drifted hundreds of mile from the wreckage. Twit.
Beacon. Twit.
Besides, what if the fuselage is so deep underwater, it doesn't really help you that the flight recorder is there with it, too?