the main reason why elevators in Hong Kong do not is that most of them are high speed high-rise elevators and the numbers just whip by. It would probably be very frantic sounding to use Morse if you went from ground to 50 in less than a minute.

Instead they only announces floors that are stopped on, so this works fine.

One benefit of using spoken vernaculars rather than Morse is that Morse has to be taught; Hong Kong historically draws large portions of its population from migrants originating from all over China, where until recently there was wide variance in schooling and literacy rates.