Why do people blog?

I have been reading different blogs for a while now. After I wrote the one entry for MY blog, the thought came to me: "Why am I doing this?" I mean, I should have a reason, an intended "audience", right? If I'm writing this for my family and friends, it will be full of my kids and all the cute things they do. Of course, then I have to tell them I have a blog, which I haven't done yet. If I'm writing this to share all my wisdom (ha ha ha), then I would write about how I'm growing in Christ and what I am learning. Or is this just an online journal? A place to share my random thoughts, the cute things my kids do, my rants about life? Am I overthinking this whole thing? Not that I'm prone to doing that. :-)