I think you could credibly ask that question for nearly anything outside of human basic needs. But the answer is simple: people are entertained and enriched by different things.

I certainly spend some amount of time on HN replying to things I shouldn't bother with, but the majority of my time on HN is filled with learning new things and hearing interesting perspectives on those things. I consider it a net positive in my life, and over the years I've gotten better at avoiding the negative parts.