It depends on the context. In my experience in advertising / agencies, graphic designers (or "creatives" as they insist on being called) are spoilt brats who found even "responsive design" too technical and "beneath" them, so much that the whole field of UX as we know it today was born to fill the gap. Expecting them to even consider using any tool other than Photoshop or Illustrator is just a waste of time. But in smaller, more "startuppy" enviroments you find some who do use Gimp. Still, the ratio in my personal experience is something like 98 - 2.

TL;DR ADobe has it pretty much sewn up