Question

why would a profit motive be good for a society?

Answer 1

adam smith stated the theory of "invisible hand" which is, people don't usually help others but improving self definitely drives benefits for others.
In adam smith's words, "Every individual necessarily labours to render the annual revenue of the society as great as he can. He generally neither intends to promote the public interest, nor knows how much he is promoting it ... He intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. Nor is it always the worse for society that it was no part of his intention. By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it. I have never known much good done by those who affected to trade for the public good."