TS, not all people can build HTPC's, and even those people who can build HTPC's like myself prefers the simplicity of a plug and play device that would play my movies, music, and photos on my large tv screen ... i do not need to browse the Internet on my tv nor download torrents using my NMT - simply just play and store those media I mentioned ... i have my own powerful desktop PC for the other stuff, my own laptop for work, my tablet and multimedia phone for mobile Internet browsing, hence my NMT is a perfect appliance for me for video, music, and photos.
If you do not have a PC/laptop and starting out to setup, I would agree with you that HTPC would be highly recommended, since it's an all-in-one device.
Disposable??? even HTPC's depreciate over time ... buy a quality NMT from a reliable vendor ... bought mine from a distributor in SG for almost 20k more than 4 and a half years ago and it still works perfectly, and much better than cheaper NMT's nowadays - i would say that it is fully depreciated now but i'm still getting my money's worth ... if i opted to buy an HTPC at that time, I would have probably spent an additional 10k to 15k for upgrades over the 4-year span to keep up with the new technology, and not to mention managing the patches and different software updates ... with NMT, it's just the firmware that you're updating