Because that's how the entire reward system is structured - ask management why they care about that stuff (money) and you will understand why people do it (money).
I have this insatiable addiction to food and shelter. If I could get over my addiction, not only wouldn’t I care about money, I wouldn’t be working.
Your apparent "need" for food and shelter is a social construct! Get out there! And by "out there", I mean out in the cold!