Working full time for a single company is a huge risk.
Being able to walk away from that company no strings attached mitigates that risk.
Being financially liable should the company go under is why co-owners share in the profits beyond salary/hourly wages.
ETA: moral/ethical "liability" included.
At least in America, being financially liable if a company goes under isn't an issue if the company was setup in reasonable way. 99% of companies are.
Less than ownership. It's a lot easier to change to a new job than to change to ownership of a new company.