1080p/i cable TV and streaming video tends to be compressed to hell now
Works OK for me on Netflix and Blinkbox. And a better compression for regular HD can't be a bad thing.
Plus, HD is still the domain of downloaded rather than streaming video anyway, for the enthusiast who spends $1000s on their TV and AV kit. And you can bet proper 4k players/discs will be out shortly.
"But a 27-30" 4k monitor for my desktop would be nice."
Um, you've been able to buy such a monitor for at least two years. The fact it didn't have a stupid "4K" sticker on it is irrelevant.