Writing is a great way to learn (whatever subject you're interested in), and of course, to learn to write well. I used to do a lot of "private writing" and just tuck it away in the file system. I don't have much patience with the editorial and publishing process. Blogging gives me a chance to resurrect what otherwise would be dead pieces. And there is no editorial process!
I highly recommend writing-to-learn, the process, even if you don't blog, or publish. I recommend William Zinsser's book of the same title. Even if you don' blog, try "private writing". It sharpens your knowledge, sharpens your thinking, and you'll have a ready inventory of writings, should you decide later to blog or publish.