I was recently shopping for a new MacBook a couple months ago and chose a 13" MBP over a MBA and a 15" rMBP for a few reasons.
First, I'm a college student. I feel the 13" MBP is the ideal size computer to carry around from classes. The 15" is just to large and the MBA, in my opinion, is just too nimble and not powerful enough to do what I need. I backed away from the rMBP because of the price and the fact that I have no real need for such a high resolution display. Also I do not like the fact that the MBA and rMBP are not expandable and lack a ODD, which I do need from time to time. However, the most important reason I declined to purchase either is because, the fact that if anything was the happen to the computer, I myself would be unable to work on a rMBP or MBA.
This 13" MBP was just ideal for my needs. The 2.8 GHz i7 is more than powerful enough and I already upgraded the RAM and installed a Samsung 830 SSD. This machine is plenty fast enough. Not to mention I save A LOT of money by picking up a Late 2011 model 13" instead of the Mid 2012 rMBP I was prepared to purchase if I wanted.
Also, I understand buying a 15" MBP or rMBP for photo editing or video rendering. However, the people that buy those $2000+ machines to browse the internet and watch movies are just sort of stupid or just have the need to be trendy.