Windows, like every modern operating system 2006 or newer, has a graphics compositor to do basic things like allow GPU-accelerated window stretching, prevent screen tearing, and so on (OS X had one slightly earlier). Meanwhile while Linux has had multiple modern attempts to build a composited graphics stack (Compiz, Wayland) certain very vocal elements of the Linux community complain about any attempt to build a graphical stack you can't send via carrier pigeon and have dragged their feet or otherwise thwarted wide(r) adoption.
