The point of all of these sites is to maximize functionality and make language information easy to get at. All that maters is UX, graphical niceties don't improve on that, and no one serious about learning a new language is really going to be dissuaded by "ugliness".
But the real answer to the title question is simple: They're made by programmers, not designers.
- The first thing the user sees is a massive wall of text. The whole site looks visually cluttered. Everything is arranged haphazardly.
- The more useful parts (e.g. the introduction, documentation links, download links) are hidden away in small corners of the site.
- The relatively useless Events and News sections take up >80% of the site.
Python's site looks slightly better, but not by much.
What about people who are not serious? As I said in my post, this "ugliness" acts as a filter to turn away non-experts. Whether this is good or bad depends on your point of view, I personally think it's bad.
Being fairly new to programming myself, I've actually noticed that the most powerful languages usually have websites with terrible aesthetics. It usually means that instead of worrying about how the site looks, most of the people involved are solving problems with the language. The only changes come when usability is hindered.