You're confusing two concepts. Even volunteer firefighters get paid, in the OP. But they don't operate under a profit motive.
The profit motive is seen as integral to the success of capitalism, in economic theory. The idea is that owners of capital will invest in ways that maximize the profit of their capital, and, in so doing, maximize the total value creation from the capital. Hence, the profit motive incentivizes everyone in capitalism to maximize total productivity. Therefore, the profit motive maximizes the gross economic production, and hence utility, of the entire system, even though individual agents are only pursuing selfish maximization of profits.
All of that is true. But it also doesn't tell the whole story.
In particular, it breaks down in two main points:
- Externalities are not captured by the profit motive. Negative externalities, like pollution, but also positive ones, like companionship and happiness.
- The profit motive is true for total creation of utility, but it completely ignores the distribution of utility. Neoliberal trickle-down free-market economic policy is inimical to equity, despite, on the surface, seeming like an effective policy to maximize total utility generation through the profit motive.
There's a whole other problem with the profit motive, too: we all have an innate drive toward creative expression and helping others. I suppose you could, cynically, say that these motivations count as "externalities", but I think that's a bit reductive. People will want to create things even without profit motive. UBI studies all confirm that people will want to continue "being productive", even if they don't need to work.
Thank you for listening to my TED Talk.
lol, high school.