You're making a huge assumption that the owner is not also providing labor. In some cases this may be true, but I would imagine that it's the exception rather than the rule.

For instance, I can be a freelancer and have to handle client interactions, billing, taxes, etc. in addition to the technical work that I perform; OR I can go work for somebody else and just focus on the technical work and make approximately the same amount (which is to say that the person for whom I'm performing the technical work is handling the other non-technical work that I don't want to have to care about).