Managing ontopicness is more complicated than just upvotes. It's a complex interaction between community input (upvotes and flags), software, and human moderation. Upvotes alone would produce a front page consisting of sensationalism and the same few hot stories repeated over and over.

Upvotes are great, because the entire point of HN is to be interesting to the community. But moderators and software are needed too. If the site were determined only by upvotes, ironically it would soon cease to be interesting to the community.

https://hn.algolia.com/?dateRange=all&page=0&prefix=false&so...

By the way, this isn't primarily because moderators are smarter or more competent than community members. It's because we're in a position to give HN our full attention and think about the global optimum. Users are giving much less attention to the site (at least I hope they are) and reacting quickly to the specific things they run across. I wrote about that here if anyone is interested: https://news.ycombinator.com/item?id=22863209.