There are far more tools for 3D content creation today than ever. As I said before perhaps you can blit in SDL but from the perspective of OGL and D3D this is not so. Blitting is 100% not available in Direct3D and requires you create textured quads to do any type of 2D graphics.
There is nowhere near the plethora of tools for 3D content creation as there is for 2D. Additionally, mathwise, 2D is downright simple, and most of it boils down to loading a few images and blitting them to the appropriate location.