Re: Beancounters
I suspect that back in the 70s there were enough "ordinary" mishaps that internal ELTs, CVR and FDRs were thought enough. The cost of wiring an external CPI and fairings didn't seem worth it, as most searches and investigations didn't need immediate answers, foul play was rare but conventional and usually obvious.
Today, in the current security environment and the rarity of "ordinary" mishaps, any mishap creates instant public obsession about the event (was it terrorism?) and demand for answers, right now!
Retrofitting a passenger entertainment system is supported by a business model, we want those movies and WiFi as SLF. The cost for a CPI would be less, if the public wants to pay for it.
If the wreck of MH370 isn't found, I think we will see something like CPIs be demanded by the public.