A general-purpose computer is a technical term that describes a device by the capabilities its components enable it to make use of in principle. A turing-complete machine. A "smart" washing machine with a touch screen, internet connection and a CPU fast enough to run Doom may be considered a general-purpose computer even though you may only want to use it for one purpose. So, it practice it's a single-purpose device, with a computer. It is this sense in which I have developed a fondness for single-purpose devices. Nowadays, these devices often end up having a computer inside them. But that doesn't mean that it makes sense to either run software other than the one provided for the single purpose on it or replace it with an (already existing) PC/laptop/smartphone/tablet/whatever. I reckon it's fun to hack household devices to run arbitrary code on them, get Linux to run on a calculator or build a botnot of smart fridges to mine bitcoins. But for daily use and the simplicity of it in daily life, I find reliable software that serves a single purpose well, soothing, comforting and simpla practical. Turn on the device, select what it should do, go. I could do without all the complexity that in modern electronics that serve mainly the developers (or their bosses need for a cheap and quick, flexible complex system).
I think many users of modern "smart" household devices would agree. But my preference for single-pupose devices goes further. My laptop and my desktop PC are connected to several home servers and NAS. It's cool to have an MPD server, an always-online, logging IRC client, a LAN-centric torrent client that runs independently from the actual terminal devices that you use. It's practical and clearly has its purposes. But, after working a more than full-time job for years, I've learned to pay tribute to the simplicity, lack of maintenance requirements and reliability of computers that are used to do just one thing. This is different from the Unix-philosophy of doing just one thing and doinf it well. I'm not talking about standardised interfaces between software components. I think that the advantages of a general-purpose media center in the form of a computer have made us overlook the advantages of standalone devices that serve a single purpose. You might have a CD or record player for music, a DVD player for movies, a notebook with a good keyboard for notes or a diary, a thin laptop or tablet for casual web browsing, a Play Station for gaming. Turn it on and it runs. No complicated and long boot process, no chance a software update might interrupt you or have broken something. Hardware buttons for the specific functions the device has. And, if a device breaks, the other ones still work.
I have askey myself why. But I really don't know why I preferr CDs over a music collection on a hard disk. It's just so much more fun to choose an album and put in the disc. Without planning to, I have started to segragate my devices more and more over the last couple of years. I have a PC for retro gaming, one for OS experiments, and so on. Doing those things in VMs is out of the question for me. Again I don't know why. But it really feels much better to have a dedicated device for some things.