Imo, the lacking exposure of "nerai" as a concept in the western world is due to the overinflated use of the term "aji" for the whole field of meaning covered by "aji" and "nerai" and ? in japanese. I would blame the inability to find a good translation for "aji" for this result.
On SL there was a proposal to translate aji as "funny business" a while ago. I very much disliked it, until I heard one of my teachers (Jennie Shen) use it quite regularly, although I didn't ask what term (chinese in that case) she has in mind when saying it. I am still not sure, whether this would make a good term, but if people use the term "aji" all around you like a magical wand, even such a fundamental concept like "nerai" is easily lost. But I have the suspicion that many people use "aji" the word for what is meant by "nerai" in japanese, while the term "aji" is what is really lost to western amateurs - or more honestly, to me.