Because people get sufficient utility from the site without changing the UX. Sure, the UX could be better, but are you likely to not use the site because of its

Because people get sufficient utility from the site without changing the UX. Sure, the UX could be better, but are you likely to not use the site because of its current form? Also, I'd argue that people who don't use HN because of its UX probably aren't going to be happy here anyway.