Most modeling applications today support Ngons, but they really aren't meant to be left uncorrected in a final model.  For the most part, support for ngons in a modeling package is so that the artist can use them as a temporary "hold" surface, which will later become replaced with proper topology.  THere are plenty of situations while modeling an object where you might want to temporarily fill a hole with an NGon while you add edges or detail to other areas, and then divide the ngon later, to complete the surface or object.  This is where ngons are handy, and help the creation of complex geometry.  It's like a shortcut to achieving certain shapes which may otherwise become a confusing or tedious process.

Leaving ngons in a model can result in many problems later on.  You could never be sure how ngons are handled in other applications or render engines, or how another artist might handle them further down the pipeline.  Ngons should never be used in real time packages, as you cant predict how they will triangulate.

Even with high end, unbiased rendering, Ngons can pose problems like self-shadowing or surface artifacts, or incorrect occlusion.  Here's a quote from the Octane engine manual directly:

"To avoid artifacts user must work only wth 3 or 4 vertex polygons."

 

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.