So I purchased a 2012 cMBP 2.9 i7 from Apple and I have a fair number of reasons for doing so.
I already had a Samsung 850 Pro 512GB and 16GB of DDR3 laying around. Even considering the purchase price for both of those new, it comes out several hundreds of dollars cheaper than a similarly equipped 13" rMBP (and I understand the arguments for the faster storage, in the vast majority of cases, I don't think it's noticeable).
I also have very poor internet service. In the United States, many of us are still subjected to satellite and hotspots for our internet access. I have 15GB of data, and utilize DVD media constantly (I would go insane without Netflix). I also have a fair number of DVDs I own, and while many of them are ripped at this point, I enjoy the peace of mind.
As far as performance, I'll point out a few things. The Ivy Bridge i7 in the 2012 model is just a few percentage points off the GeekBench performance of the current rMBP's i5. Certainly GPU performance on the new model is far better but, unless you use a lot of visual applications or games the difference is pretty unremarkable in daily use. The i7 and the HD 4000 has no issue driving a 2560x1440 display and working through day to day tasks just fine. Never does the machine feel like it's struggling to do the things I do, and that includes a fair amount of encoding videos.
However, I'm not delusional. If the money is of no concern (or the DVD drive and expandability), then the rMBP is an awesome awesome machine. It's thinner, has better battery life, has HDMI out, etc. The screen might be worth it to most.
I honestly thought that it was pretty clear why the cMBP still sells. It has the build quality, the style, most of the performance, and it's relatively cheap. I do also understand why a lot of you find spending that money on "old" tech objectionable. It just didn't matter much to me once I looked at the actual performance.