An argument can be made that all actions people take are for their own self-interest. Even things like helping the community is done for reciprocal benefits for yourself plus the general increase in respect.
Another point is that if all people just act for their own self-interest, they will have a better life themselves, and if everyone does the same, some sort of proper balance will be achieved.
I have been having some occasional discussions with my friends over this. I personally disagree, but would love to hear what others have to say. Feel free to discuss!
Autistic people will often do the right thing simply because they were taught it is what they are supposed to do - with no consideration of how they’ll feel about it.
And ADHD people don’t get to feel good about anything they do.
Combine the two and you get the ultimate altruists!
(this comment is meant as a joke)