Like many others have already said, we have family and friends out of town, and it is our way of keeping in touch. Also, I like to have a place to share my rare "epiphanies" about life, God, homeschooling, etc. I've been inspired and encouraged by the blogs of other moms(and dads) and hope that I sometimes can offer encouragement and inspiration as well. I try to keep a running log of what we accomplish in school every week or two.
Everyone views blogging so differently. Some people are insistent about posting daily while others only post when they have news or an update. I try to post a couple of times a week, at least, but I definitely am not consistent.
I would encourage you to give it a try and see how it "fits" into your life. You may find you really enjoy the outlet.