But why is this so-called "greed" less acceptable than the "greed" of owners/investors, who want everything be as efficient as possible for their own benefit?

But why is this so-called "greed" less acceptable than the "greed" of owners/investors, who want everything be as efficient as possible for their own benefit? Strong organized labor is how we accomplish "inefficiencies" like paid leave, regular breaks, safety standards, etc.