- The study of ethics is inherently valuable. Regardless of what other studies tell us about "what to do" or "how to do it", we must assign some value or priority to our actions. You could try to use the findings of any other fields of study to guide your decisions. With psychology for example, we can study what makes people happy, and base our priorities on that. But ultimately you've just made an ethical decision to act on utilitarianism. It's inescapable that we make some ethical decisions, so it is worthwhile to study which ones are "best".

- Philosophy does not exist in a vacuum. In the same way that a work of art can lift someone's emotions, teaching and studying philosophy has real-world consequences. Had Hegel's works never been published, the world may have never seen Marxism, as one very big example! It's worthwhile to study philosophical theories within their own language and internal logic to understand the impact that they have on people. E.g. it is helpful to study Ayn Rand's thought itself, and not just the way it affects people's psychology, or the effects of its political applications. For example if it can be disproven by it's own internal logic, that has implications on its applications - we don't need to apply it to any political calculus to determine "P is not P" is false.

Sorry if my explanations aren't that great. I personally don't study philosophy, and can't offer much more from the top of my head, but I believe my apology of it so far is sufficient to at least say it isn't useless!