Well my opinion is going to be a little biased but lets see.
People have blogs for a variety of reasons, to record their thoughts, share with others, keep in contact with friends lives, share their ideas and what they think is interesting, etc.
Everything on the internet is a wasteland of repeated information. The questions asked here are the same ones asked at the hardocp forums, which are the same ones asked on usenet, which are the same ones asked on mailing lists. You get different viewpoints from different people for both though. The internet isn't about having a book with one correct verified edited answer, its about open communication among people, so you're always going to have this and its a good thing. If you want to talk about clutter lets talk about spam, the joke emails that everyone is always forwarding to me, etc.
It isn't a substitute for personal home pages either, there are 1000s of tools, both downloadable and web based that help anyone create a crappy page for putting up pictures of their 36 cats. And there are certainly enough of those types of pages to show people have no trouble creating them.
Personally I keep a semi-updated blog and photoalbum up. Part of it is I enjoy writing, and I enjoy sharing my opinions. But I also have friends that read it, family that I link to the pictures, etc. If you want one source of information then go get a dictionary set, but I like blogs because I can interact with people (much like on a forum...).
You asked, I think its only fair if you answer your own questions too.