Walt wasn't hesitant to show what goes on behind the scenes and how things were done at
Disneyland on his TV show. It made the attractions the imagineers came up with, IMO, that more magical. To think, what was their creative process and how did it evolve into what we enjoy today.
Not sure when this "let's hide everything" mantra came into being. If kids were more exposed to the workings of the parks, they might be inspired to learn more about the technology and creativity that went into building these beloved attractions.