Yes, that's a good question. I love to read other people's blogs. I really do. I probably visited your blog today. Or yesterday. Maybe it was the day before.
I'm awful, though, because a lot of the time (ok, I won't lie, most of the time.) I don't leave a comment. It's not because I didn't like your post. It's simply because I just didn't know what to say.
Blog commenting reminds me of when I was back in high school and it was yearbook signing time. Someone would bring their yearbook over and ask you to sign it. The comment had to be fantastic because it would forever be etched into the history of this person. The same with blog comments.
I crack under the pressure.
Someone needs to create an acceptable generic blog comment that you can leave that just simply means "I was here. Loved what I read. Will be back to read more later." At least the blogger would know their time and imagination (or whatever else goes into a blogging post) didn't go unappreciated. All pressure on the blog reader would be relieved. Antidepressant sales across the world would weaken. Wine consumption would decline. No more blog comment duress. Hallelujah!