Because business don't have employers, they are employers.
I am thinking of me as an employer.
Have you ever owned a business?
I have, and do now. I am an employee of my own business. Companies pay my business for services that I render and my business pays me.
Companies, although they don't pay payroll taxes on my services, still have to pay for them, corp to corp. My business pays me the lowest wage possible to cut back on payroll taxes-- the remainder in dividends.
I can't just suddenly declare myself to be a business, though. If I did, I would find myself as Martha Stewart's cell-mate.