The owner gets more control - both on the company, it's long term vision, it's investors and the future of the company.
It's a win for all.
What advantage does being public get you?
It gets you $ at a massive cost - both regulatory and quarterly.
Apple is owned by countless pension funds, endowments, likely every politician who invests, and a large % of the general population.
Their success is also part success for all those people. Private companies have far fewer defenders, much easier to vilify and punish.