Why do you think NVidia keeps up-to-date drivers with great CUDA and OpenCL support for Linux? For all the Linux games on utilizing those technologies? Of course not, those technologies are however heavily in use in the aforementioned markets, of course HPC in particular.
And these markets are getting even more important for discrete GPU vendors like NVidia as the end user desktop is moving away from discrete GPU's to GPGPU solutions. Also since NVidia can't get a licence to produce their own GPGPU solutions on the x86 architecture the x86-based user desktop is becoming a dead market for them as their days there are numbered.
Of course they have the ARM platform which they are now focusing on, and the future battle on mobile devices between Intel's new low power offerings versus ARM will be interesting to watch. Personally I'm rooting for ARM for no other reason than that I really want competition.
And just so that those who think NVidia 'rules' the desktop, here are some 2012 first quarter numbers to ponder: