What is wrong with embracing the grain as an artistic expression?Nothing at all.
But when you're hired by "Glam Magazine" to do a nighttime outdoors photoshoot and they want clean image for their feature article, you might want to deliver what they're paying for. Just saying that I too think artistic grain can be quite nice. But when looking at photography from a profession's standpoint, the public has their own idea of what a "good photo" is, too. And often times, grain isn't a part of it.
Sometimes I like grain... sometimes I add more on purpose. However, I want that _choice_!
If your equipment is capable of a clean image... then it gives you total artistic freedom to add grain where you see fit... instead of being forced into it by an inadequate sensor.