Owners can be anonymous shareholders who don't contribute any work, but speculate on the ability of the business to generate capital gains for them. While it is true that owners can do some of the work, they utlimately hold the economic privileges that determine how the profits are going to be divided (and how much economic rent is to be collected in the first place). That leaves scope for exploitation, though it doesn't guarantee exploitative behaviour.

I'm fully in favour of people profiting from the work that they do, so long as it doesn't harm others.