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!
As with many things, I think the answer is somewhere in the middle.
You have to act in your own self interest at times otherwise no one is going to prioritise your interests. But at the same time you should at times prioritise other peoples interests so that they will do the same in turn, I love the saying, “treat others how you would like to be treated”
That said, if you only ever prioritise others over yourself, at some points this will be a detriment to you.
However, just because you might try and strike the balance of maintaining your own self interest in tandem with those you care about, doesn’t mean you’ll always strike the right balance or not accidentally prioritise yourself at the detriment of someone else, we are only human after all.