I can't imagine how painstaking it is to do every frame through the panning camera backdrop, and the amount of work gone through the planning phase. It definitely seems like Disney invented interesting technologies back then.
Animators didn't want to draw all the backgrounds slightly moving and this allowed re-use and new innovations to make movies faster. This allowed animators to focus on the character cels and making characters look better, the main focus.
The multiplane camera with movable layers for parallaxing directly led to some of the best early Disney movies (Snow White and the Seven Dwarfs, Pinocchio, Fantasia, Bambi, The Adventures of Ichabod and Mr. Toad, Cinderella, Alice in Wonderland, Peter Pan, Sleeping Beauty and The Jungle Book) and helped their budget as well as made them look better. Plus at the time, it was actually an improvement that animators welcomed to speed up their tedious work.
Or better still, "Digitize all the artwork for each plane and composite them in a computer!"
Seriously though, it is amazing what patience and ingenuity can accomplish.
Seriously, though. Despite having seen this video before, I am glad it is posted again.