I don't have the need for mobility anymore. I work from home. I can build myself a beast of a machine with 60% of the cost of this desktop or an iMac. Don't get me wrong, I love my iMac but it beachballs way too often; enough for me to notice - and it's an iMac from Feb 2013. To me that's sort of unacceptable given the price I paid for it.
I then built myself a desktop with $1000 and it's a beast, full SSD 16GB ram the works. Never stalls, always keeps up with my chain of thought. You would think it doesn't make the difference but it does and it's noticible.
That's a great reason. I did the same back in 2009 when an iMac couldn't support the displays I wanted along with CPU/RAM requirements. I find my computing drifts when I do that — I end up with a lot more flac music that doesn't port back to iTunes easily.
But these days, I can grab a rMBP, hook up three 27" external monitors (plus the built in 15" HiDPI display, plus the rMBP can use an AppleTV as an external monitor, not just a mirror now), have a 1 TB internal PCIe flash setup, have 16 GB RAM, and four 2.6GHz (~8 with HT) cores to do my bidding.
Plus, the Linux box was about two feet tall and acted as a noisy space heater even in the summer. :-\ (but, I had it crammed full of 2 TB drives. but, rMBP has USB 3 and Thunderbolt for easy expansion. It's more difficult for me to justify large computers for non-compute-intensive tasks these days.)
But, it's smaller, outputs less heat overall (though, the keyboard is often too hot to touch if you rest your hands on keys or—god forbid—if you accidentally touch metal between keys), and it sometimes stalls all display output for 30 to 60 seconds at a time while running all cores at 100% for no discernible reason at all between once a week or 15 times a day depending on its mood.
Let's see your tower do that.
Stockholm Computing Syndrome?
As far as price: company bought it. Always change jobs right before an Apple hardware refresh event. If it wasn't essentially "free" from my end, I'd have gone with a 27" iMac.
Why not? There aren't any alternatives.