Because the points system replaces online the offline signals you, and we all, use for just that non-thinking - signals like facial disgust, like if a restaurant is full or empty, like other people in a room taking notice of one person.

we need social signals to determine how the society we are in is functioning. points, likes, follows are very poor proxies - but we need something. if those proxies are making billions for some people that's not the fault of our need for social alignment.