Why don't candidates blog?

I was a little excited when I first saw Gregg Knaupe's blog, but then after I started reading it, I found most posts were from his campaign manager. And the few posts by Gregg were more PR then his opinions/ideas.

I would like to see a candidate who's a real active blogger: who does his/her own posts every day, who's not afraid to give his opinions and ideas on issues, who has a blog with comments enabled so ideas can be exchanged.

Just think if candidates could do this. The public could really get to know their candidates without the candidates having to spend tons of money.