Just because there were driver issues at launch
Thats [censored] ZeniMax just didn't test the game on PC. If they had they would have had the problem fixed before the release of RAGE. If they did test it then would they have not brought it to the attention of GPU developers before its release?
I am sure RAGE is not the only application to use the specific programming calls where the bugs are occurring, so if it was a driver problem, then the problem would have been reported to GPU developers yonks ago.. so, this tells me that John Carmack needs to brush up modern OpenGL.
... and for those that want to continue keeping their head in the sand, whats the chance of two GPU manufacturer drivers being "buggy" over one application? Tiny! No..! Zenimax justed didn't bother testing the PC version - more evidence this movie/bankster company doesn't have a clue about making computer games.