It is always better to be able to exploit terrain, circumstances or human psychological tendencies than to fight against them. In this we can speak of the brilliant discovery of liberal economics. Not to repress human egoism, but to harness it so as to serve the common good. This is the famous story of the baker who was driven by his desire for profit to bake the best bread rolls.
But centuries later, it turns out that comes with its own set of problems. First of all, there is a very narrow line between exploiting egoism and encouraging egoism. And egoism is never completely unshackled, there are always some downright destructive elements.
Besides, thanks to neuroscientists and their research, we know that man is not that egoistic a being unless he is downright encouraged to be so.
Some people, under certain circumstances, are. But many others are selfless and willing to help. And there are those who are willing to make the sacrifice just to see selfish people punished (so much so that the sight is satisfying to them). Most of us have a mixed bag somehow, the situation, habits and feedback deciding.
By the way, for the vast majority of people, if they help someone, it brings them more satisfaction than anything else. We just often don’t know it ourselves. We don’t believe that selflessness can bring us joy, and so we act irrationally.
In short, it is often useful to motivate people by encouraging healthy egoism. But often it doesn’t work, and sometimes it is even destructive.