The argument that an event is unlikely and therefore not worth planning for I find a bizarre argument in the airline industry and likely a worrying one from a customer point of view.
A plane may ditch successfully
(it's happened) and there be survivors
(it's happened) who will drown because SAR can't locate the plane
(it's happened) in time .
I find nothing unrealistic about that comment, anymore so than needing all sorts of backup systems we have on our planes which will likely never be used.
The whole modern ethos behind aeroplane design is redundancy after redundancy for a very good reason. Yet some here are actually arguing that a foolproof system to locate a crashed plane is a crazy thing to develop.
I don't care about planning for the 400,000,000 flights a decade that go to plan, I care about the 1 that doesn't.