You mean Windows. KDE is iffy (but I use it just fine and was able to scale my fonts / frames up enough on my 150 DPI notebook), but Gnome in its latest release has fantastic high dpi support.
It is an unmentioned consequence of Windows being a piece of shit in regards to DPI that holds back the desktop display industry, whereas Androids inherent scalability let smartphones race for big pixels.
Ah, Windows* is catching up. But the ecosystem (third and some first-party applications) has been admittedly quite slow in making their applications HiDPI friendly. Metro/Modern apps for use on smartphones and tablets is already quite good, desktop apps are catching up.
*disclaimer: MS employee who is just enthusiastic about "viva la resolution."
EDIT: 4k on ~30" is too high resolution. 4k on ~40" is too big/wide.
Also, for the same price, you can get the same 28" 4k Samsung monitor from Amazon (search for samsung u28d590d).