Windows 8.1 has keyboard shortcuts to make a window take half the screen, the full screen, etc. Hold down the Windows key and try the various arrow keys. You may be pleasantly surprised.
There are all sorts of other useful shortcuts that use the Windows key as a modifier, for example Windows+E to open a File Explorer window. Basically, try Windows+(every key) to see what it does.
I'm aware, but until the majority of people are using a system where basic window management exists, vendors have little incentive to sell double wide monitors because so few people would be willing to use them. So those of us who can make good use of them have to wait forever, just like we did for reasonable DPI LCDs.
Also, even in the newest windows it is still crippled. Applications can prevent themselves from being resized like that, and often things like games that you would want to run in borderless window mode can not be moved around using windows shortcut keys.
There are all sorts of other useful shortcuts that use the Windows key as a modifier, for example Windows+E to open a File Explorer window. Basically, try Windows+(every key) to see what it does.