You can call it flexibility, for a lot of people it might simply be cost per GB, ie, you can get to 1 TB internal storage much cheaper with this 2012 model ($1150 vs $2300). Even to get to 1 TB of SSD internal storage, this can be done much cheaper via third-parties ($1400 vs $2300). And even if you added the faster processor (to reduce the CPU power gap) and increase the RAM to 8 GB to match that spec, you'd be still much cheaper ($1600 vs $2300). You could even go nuts and add two high-end 500 GB SSD in a RAID 0 (which would get you into a similar territory in terms of performance) and still be cheaper, including the CPU and RAM upgrades ($1900 vs $2300).Well, they still sell an un-updated 2012 13" MBP.
Although to be fair, I'd buy that over any of their current machines (since I need the internal storage flexibility).
Though, if I wanted to get a 13" MBP with 1 TB SSD for less than $2300, I'd get a used 2012 13" retina MBP (about $900) and upgrade the internal SSD to 1 TB via OWC ($500). I'd be stuck with 1 TB (though higher capacity upgrades might become available) and likely 8 GB RAM (most people got that 2012 13" retina MBP with only 8 GB) but I'd get a retina display (which would be worth the risk of something breaking earlier in a used device).