Lol!
Well, you see, it's like blog sites. Very few people know even the basics of webmastering, compared to the huge amounts of people who want a website. Using a CMS is like being a client telling to a webmaster "I want this and that on my site, now do it". And since you're not paying him you never get more than what you ask, and of course you can't ask too much either
You actually get a lot of built in features (forums, news, blogs, galleries, polls, chats, templates, the list goes on...), but in my opinion your site loses all its essence, it has no "soul" anymore. It feels like you're on someone else's website, renting space to put up your own stuff.
It can be a pretty good start to see the mechanics of a website, but the coding is usually so complete/complex that you can't really start learning from that anyway. I really just see it as a Beginner's guide to
having a website (not making one).