Why? Because ngons will make their offline renderers explode? If it looks good, it is good. Game art, pre-rendered cinematics, it doesn't matter. This "use quads for sub-d" has roots in ancient/poor software that litterally could not sub-divide triangles or ngons. Unless you have some extremely specific reason to only use…
Well, I did use subdiv modelling in the past but once Zbrush got sub-projection slider in its dynamesh and a density picker I gradually stopped to do subdivids at all. Then a few years later I stopped to do hi res models for hard surface things too mostly because of rounding corners shaders + adding details straight inside…