That is for two reasons: One, only rich people used to be able to afford gelatin dishes as it was a pain in the ass to make fresh; and two, a lot of people had no teeth back then.
Making regular gelatin is like a 10 hour process, so that makes sense. It is also almost impossible to get the meat flavor out with the regular method so enjoying beefy lemony gelatin is probably not everyone's cup of tea.
There was also a hilarious "putting shit in jello" phase.
That is for two reasons: One, only rich people used to be able to afford gelatin dishes as it was a pain in the ass to make fresh; and two, a lot of people had no teeth back then.
According to this video its popularity can also be attributed to wartime rationing and ease of cooking.
Making regular gelatin is like a 10 hour process, so that makes sense. It is also almost impossible to get the meat flavor out with the regular method so enjoying beefy lemony gelatin is probably not everyone's cup of tea.
https://www.leaf.tv/articles/how-to-make-gelatin-from-animal-bones/