Why is "fitting in" so important to NTs? Basically because they're insecure and easily feel threatened. That's the $1 answer. The $20 answer is this:
Quote:
Neurotypical individuals show difficulty in forming an individual identity, or in thinking outside of the bounds of the accepted norms of their social groups. It appears that each group a neurotypical belongs to will have its own set of "official" opinions, and each neurotypical within that group is expected to adopt those beliefs. As strange as it sounds, they generally do so very readily, and are not hesitant at all to help enforce those beliefs and ensure group homogeneity of opinion. There appears to be an innate drive for the neurotypical to fit in with groups in that manner, and their own innate opinions and desires are modified automatically to fit the group ideal. This bizarre lack of independence explains the tendency for neurotypicals to engage in fads of various sorts, or for the existence of certain trends. Neurotypicals will change the way they talk or dress according to these trends, and other neurotypicals will admire and imitate such "trendy" behavior. As such, neurotypicals are easy prey for TV commercials or other means of advertising that seek to portray the purchase or use of various products as socially desirable or "cool."
The need for neurotypical individuals to "jump on" the latest trend is a function of their excessive level of concern of how they are perceived by others. Neurotypicals form their self-image based at least as much on the opinions of their peers as they do on their own opinions. They do not perceive themselves as individuals in the manner that you or I do; they see themselves as individual members of a group, but in practice, the opinions of others weigh heavily upon them, and there is a great drive to obtain the acceptance and admiration of others around them, including complete strangers. There is a built-in tendency for neurotypicals to blend in, to become "one of the herd," so to speak. Most of them never realize how much their opinions are dictated by the group. They want the things that the group deems desirable, and they internalize that desire so fully that it feels to them as if it was an internally-motivated desire.
That's taken from here (
http://home.att.net/~ascaris1/neurotypicality.html ), and was presumably meant by the author to be tongue-in-cheek, although I find it pretty accurate.