I don’t know the history, or have a reference, but I once read that on a query to the manufacturers, as to why they were so expensive to fit in aircraft, the answer was they have to be stressed to carry in excess of 250 kg.
When the manufacturers were asked “why” since babies do not weigh that much, the answer was that since they are located in the toilets of the aircraft, they are often used for activities, more in keeping with the production of babies, than changing them.
It would be interesting if that could be confirmed either with manufacturers or aircraft fitters that service them.
Best of luck with your research.
