Many people (in fact more than 50% even in the US according to cnbc [1]) live paycheck to paycheck.
Not to mention that spending structure change over time. Back when I was 20 - I only needed that much money to buy myself some food and drinks, a pair of sneakers or boots once a few years + some here and there spending. Nothing big.
Now I need to provide for my kid, wife who is on maternalily leave and I need to save some money for my mother (call it her additional pension) and my family because you can really have a family and no savings. God knows what will happen.
And if you have a kid (even one) - you need to spend a ton of money on clothes alone. They grew really fast, they get dirty when they eat or shit (in case diaper was put in a wrong way at night for example) etc.
Unless you are really rich - you won't be able to leave your job for long. I can imaginge 3-6 months leave if you are a Senior Developer or higher and you live in a country with stable economy\political situation.
In any other case - I doubt anyone will take such risks unless they are literally about to go insane or something.
The fact that most people do it doesn't mean that _you_ as an individual have to do the same. Source: 40, 2 kids, single earner, could retire anytime I want.
"Could" is not the question here. The question is quality of life and for many people in many countries simply access to rather basic goods.
It's great that you can just retire anytime I you want, hopefull without any downgrade for family's well being. I'm just saying this is not always on option.
Maybe that's true up until you have a kid. Once you have a kid, spending expands as the kid does.
Baby require nothing but clothes, cheap food and love.
Teenagers require all sorts of things for school and activities. I mean, technically you don't have to provide them, I guess, but if you want a well developed kid who will have their own success, you have to do some investing.
And if you family is "wife+N small kids" - you can't really leave a job for long. Even if you are an IT guy with a good salary.