The idea came from a British guy called Robert Owen in the 19th century. It was a huge step forward in workers rights seeing as it was fairly normal for factories to work from sunrise to sunset to try and maximise their output.
Typical working hours were 10-18 hrs a day 6 to 7 days a week
I'm not saying I love working 8hrs a day and modern society can definitely do better but this was a positive step forward in history and should be celebrated... celebrated isn't quite the right word but I hope you get what I mean