I see it differently.
Some people are here to serve themselves. (STS)
Some people are here to serve others. (STO)
I learned this dichotomy a few years ago while learning about something that I now think is false; that being, Nibiru.
However, the dichotomy is real. While learning about the above, I decided that I was part of the STO faction. Many of my actions are done because they are the right thing to do -- rather than that they benefit me. In fact, I tend not to maximize the potential benefit to me in my interactions with others -- which is one of the reasons my wife decided to take my ring.
No question some are looking to serve their own interests. The hard part is figuring out who is doing that vs being here to serve others.