If this is how everyone would act in their daily life, you would see crime, theft and abuse on an unimaginable level. No, people don’t always do what benefits them “at every individual point”. We are social creatures, acting as a community where the individuals benefit from working together. Although this has been successfully undermined by capitalism and other hierarchies.
This whole concept is also called, the Prisoner’s Dilemma, one of my favorite thought experiments because it shows how being rational can result in everyone being worse off.