Blogs vs wikis

I have recently introduced blogging to a school in this region and have been impressed with the uptake of the tool. While they had been using wikis for admin purposes, they hadn't really used them with their students. Blogs on the other hand have made an instant impact. Teachers are posting student work, class photos etc on class blogs and parents are making comments in return. My question is - Why? What is about blogs that makes them more popular than wikis? They seem so much more one directional than wikis, yet this school instantly took to them. My hunch is that it's about the visual appearance not the functionality. Blogs are tidy and have wallpaper options that wikis don't. They are organised and have lovely straight lines, not my chaotic bounce off the walls thinking but perhaps this appeals to more traditional teachers. Or am i being a bit harsh... I'd welcome some comments on this phenomenon.