Because you are not the main character of the universe.

You will leave behind consequences for your actions. The consequences of the actions of others gave you the world you have lived in, as will the consequences of your shape the world of the future.

There is nothing after death and we all know that, so all there’s left to plan for after you die is the legacy of what you did while you were here.

Speaking for me, I value the idea that the consequences of my life wind up being more positive than negative for future generations. I also value feeling like I’ve changed things for the better now, and so when I have a platform or any influence I aim for that.

If you don’t care about any of that, please seek counseling. The rest of us will be better off with fewer narcissists.