Shouldn't JFK be named Idlewild? JFK was only named JFK in 1963 afaik?
Remember this is a game, not a historic simulation, so some things are done for ease of programming, ie Bush Reagan and Kennedy airports
Airport names can only change, if the airport closes and re-opens due to the way the system works.
As know on the airport changes in NRT, GRU, etc. the demand tends to go haywire when this happens. Also it would be overly complicated to change it.
Albeit many people today don't even remember those days, when the airports had their old names. - Remember, New York used to be New Amsterdam at some point....