Because in a world where everything decays, including most physical objects and your health, your ideas preserved is the only thing that may remain of you in the end.
I've developed a pretty unqiue approach to naturalistic non-arbitrary universally binding morality that has fixed my Ai alignment issues (without being able to retrain their model off their weird utilitarianism), but I'm not highly motivated to share it, it'll get around eventually if humanity doesn't implode.