If you "work harder", you will be compensated fairly. Of course, "work harder" is overrated now that work doesn't involve physical labor. "Work harder" has been replaced by "create more value".
The expectation is after you create more value for the owners, you will be compensated fairly. If you believe that, go talk to engineers who worked on startups as early employees and got screwed by investors, founders, managers etc.
Why? For many reasons:
- the owners didn't think you could do any damage to their reputation and impact hiring prospects after they screwed you
- after the company grew, you were now interchangeable
- needed to raise more money and dilute your shares
- you were no longer as valuable to the next stage of the company
- They didn't believe you could replicate the value you created again
etc.
Of course, founders, investors and friends stick around regardless of the stage of the company or the value of their contribution. Why? Because they OWN it, they have power.
Do not confuse performance for power. The only time I got a significant raise (I mean 4X the pay) is when I had significant leverage. Opportunism, self interest and politics rule business.
People are not gonna give you more money if they can avoid it.