It comes from how technology has worked in the past.

Think of how the steam engine and industrial revolution took away hundreds of millions of jobs. How every leap in technology replaces the need of thousands of workers, freeing them up for other professions.

If you follow this logic forward, you end up at a point where labor is entirely replaced by machines. It isn't too far fetched, as jobs are already being replaced with bots, and anything you can teach a person, you can make a bot to do the same thing and instead of costing minimum wage, it costs pennies of electricity. There are exceptions to this, but those are being eroded away as time moves forward.

Eventually you run out of professions for people to be freed up for, and you end up with an employment crisis. We tied the ability to live directly to employment, and now that system and the progress of human technology are at direct odds with each other. If tech advances, people lose their jobs. The problem isn't that they lose their jobs, it's that their ability to not starve to death in the street is dependant on their employment. When there's more people than jobs, and no system to deal with this, those people die.

You solve this in 4 ways.

1. You let them die.

2. You create jobs for jobs sake (basically menial labor that is meaningless, but exists so people can be employed)

3. You stop technology. This is simply impossible.

4. You decouple the ability to survive from employment, and use the surplus generated by the mechanized economy to allow people to live as they wish, while machines and bots do the work.