Why not fully responsive?
The main reason I decided to not do a fully responsive theme was mainly because of two reasons:
1. Ads. On fully responsive themes, the advertising tends to get taken out or displayed at the very bottom of the page to make all the content fit. When an organization depends on advertising as its main source of revenue, this is a bad proposition to entice advertisers.
2. iPhone/iPad “reader” button. When you’re on a single article page, the iPhone/iPad has a “reader” button that shows the article in a super easy to read way where the article is front and center. On a site like this where the main focus is the content, this is a far better way to read than using the responsive method.
These are all just my opinions of course, but that was my though process for deciding not to do 100% responsive.