the benefit is that you have increased output.
I can now use the same strategy towards a worker. I can say that in order for my products to become cheaper so that he can buy more of them, I propose that he works 20% more time for a slightly lower wage. The logic is the same. If the guy tells me: "hey, you propose me to work more and earn less ?" I will answer him: "but my dear, your benefit is that you have increased your output"

Its a macro concept not micro
As long as output scales with extra work time you are correct, but generally workers operate at top capacity, and lack the ability to grow to meet higher demands.
Companies on the other can scale better, and with growth, comes efficiency, this is why output matters.