How old were they?
Why had they never observed, or been instructed by adults about, typical elevator operation?
Had they never seen an elevator, but had played video games? Was the display of the elevator's current floor close enough to the buttons, or perhaps stylized enough, to suggest it could or should be directly controlled like a video game character?
(Perhaps JGC was performing an experiment with a young child or recent immigrant?)
I think the traditional design was probably optimal at the time it was designed. As others have noted, a single call button adds unnecessary stops -- and at the worst times, when the elevator and lobby are most busy.
Many times there is no indicator of where a elevator car is. Or, in different buildings, variable numbers of cars, unrelated to the standard up/down buttons. So anyone with experience with a few different elevators will find interpreting from their location, rather than the elevator cars, the more consistent approach.
Apparently the state-of-the-art is to have buttons for every floor to be outside the car, in the lobby. Each person declares their destination with a press; as cars arrive they display or announce where they'll stop so the right people can board. But elevators are an old technology; so many buttons and such optimal grouping/scheduling were impractical when the current conventions arose.