Hey, we newbs can contribute SOMETHING--namely useful content for other newbs (that rises above the noise). Newbs have to learn somewhere, and if experts aren't contributing, then to whom do we turn?
As far as I know, most Wikipedia articles were mainly written by students, not experts.
Staying in a beginners mind is hard once you have spent some time with a technology. It also sometimes offers great points for the experts what could change, because it could be easier or is simply unclear.
Of course there are very simple-minded blogs with practically no content, but there are also simple-minded Github accounts that offer practically nothing. There are CVs for the same purpose. I don't think this has anything to do with blogging per se.