Why?

Why?
"Because we can" is not a good enough reason.
It does not seem reasonable to me that we should put information on the internet in blogs or web sites unless we have something to say that may be of some use or relevance to others. The assumption is that other people will read it or we would not be putting it in the public domain in the first place.
The danger is that we have the potential to load the whole thing up with waffle and many blogs appear to be very good examples of that. The response by 99% of people to a lot of blog content is "and your point" or "who cares".
Well hopefully someone does.
Library people are big on "authority" and require authoritative credible information sources. This has made the internet tricky to use at times as you need to be constantly aware of the importance of checking the authority of the source.
This leaves many blogs out in the cold as valid or reputable information sources. On the other hand as sources of entertainment or as the electronic equivalent of "light reading" the blog comes into its own. I guess it is more about communication than information.