Why people run these? What does it do and what could be the use?

I install it and then what?

1) install nanoclaw in docker 2) ??? 3) profit

More seriously, set it up as you would a junior employee with a high quality getting started guide, guardrails, and clear feedback loops that it's doing tasks correctly (otherwise it will just suck). Then delegate tasks to it, start simple and grow in complexity as it demonstrates it does a good job on the simple tasks.

What role it does for you depends on your business, and what is best fit for automation. Purely digital roles with good feedback loops are the ones I focus on.