Monitors are stills...
Still camera imagers are very cheap, monitors not so much. The economies of scale on monitors follow consumer video, at least to start with. In the early days, computer monitors were precisely PAL and NTSC monitors. They evolved upward from there.
Today, consumer video is nominally 2K (1920x1080, close enough to 2000x1000). There is already a move in cinematic video to 4K (nominally 4000x2000). You can get 4K monitors today, at a professional market price. If you want consumer prices, you'll have to wait some years, for consumer 4K to start pushing out today's 2K/HDTV stuff.
As for stlls.. you're supposed to make prints from your 20Mpixel DSLR, not view it on a television. Some people.. yeesh!
