It becomes important with low resolution framebuffers and once things start to move. Triangle outlines in early 3D games tended to wobble and jitter because the

It becomes important with low resolution framebuffers and once things start to move. Triangle outlines in early 3D games tended to wobble and jitter because the 'math' didn't work at subpixel precision (many PS1 3d games suffered from this). With subpixel precision (e.g. you do all the math at a higher precision than the framebuffer resolution, and preserve the fractional part of pixel coordinates in all computations until you actually write to the framebuffer), the outlines remain stable even for small movements. IIRC Quake (with the software renderer) was one of the first games which paid proper attention to subpixel accuracy, and they showed this off with a very slight camera movement at the result screen after a multiplayer match. Triangle edges were properly 'crawling' instead of being all jittery.