and why would I want to do it?
I have been looking at various books on Amazon (there are millions of em) that make all sorts of claims in their description but how on earth does anyone make any money on this and again why does anyone do it?
I am not being sarcastic I am just really curious.
There are a lot of people who work very hard to make money from their blogs. It's not only possible, but it's relatively easy to generate a modest income from a blog. Just do a quick search for "monetizing" a blog and you'll get TONS of information.
But to answer your question, I wouldn't consider that a reason to blog. I started blogging because it was a convenient way to chronicle my training. I continue to blog because I enjoy it. It's creative and it has allowed me to network with like minded people throughout the world.
It's also my space. Here, I follow (well, I try very hard to follow) the stated rules. But on my blog, I can say what's on my mind. Of course, nothing happens in a vacuum. I can (and have) written articles on how to correctly clean a gi, with a few reasons included about WHY it's important. I can give my sense of humor some exercise, or write about something that's been bothering me.
The difference is that, on a blog, while it can generate conversation, the intent is different. Here, I would presumably start a thread to generate discussion. On my blog, I write an article for its own sake, and if it generates discussion, that's a by product not a goal.