It's hard to form a comprehensive opinion about a subject without writing about it. My blog helps me do that because it forces me to research the stuff that I believe to be true and write concisely about it.

If the blog helps you form your ideas, it is worth it.

If the end goal is to have a readership, be prepared to do more than just writing. You can easily easily fall in the trap of writing to please your audience. And they can steer you in unexpected directions.