One of the rarest and most under-appreciated skills in tech is the ability to explain things. As an industry, we mostly focus on building and selling, and the twain don't always meet. Many of the builders have deep and excellent understanding of the tech they work with; many salespeople are excellent at persuading customers to do x. But there's a very important and underused bridge between insiders who understand, and everyone else. Blogging is a great exercise for deeply technical, because it's a chance for them to actively ask themselves: What do others not understand, and how can I explain it clearly?
"If a thing be really good, it can be shown to be such. If you cannot demonstrate its excellence, it may well be suspected that you are no proper judge of it."
Unfortunately, I don't think blogging improves this skill unless you get someone good at writing to review every post you make.
I read (or rather, try to read) plenty of poor technical writing linked on HN and Lobsters every week. Because a lot of people blog as a form of self-documentation and to improve their "personal brand" activity, people rarely give or listen to writing criticism.
