http://bugs.winehq.org/show_bug.cgi?id=18074
--- Comment #24 from evanh evanh@clear.net.nz 2010-08-01 17:33:31 --- Heh, I bet if you try to use Intel's Windoze OpenGL driver you'll find it is just as limited as their Linux version.
It's likely a simple case of Intel have only added shader support relatively recently to their hardware and Direct3D driver due to demand. That same demand is not there yet for OpenGL.