I might also ask, why do I breathe? Answer: because I can.
I don't have a specific reason as to why I blog. I don't do it to keep in contact with friends or family, nor do I have a specific topic I blog about. I find myself typing up a blog whenever I come across an interesting website or discover a story to share. It's not quite a journal because I don't share very intimate feelings. However, I do share my opinions.
I think I blog because I have a desire to be heard--or in this case, read. I don't care who reads what I have to say, I just want them to know I exist and have things to say.