Hey.... coming from a girl who rides.... I just knew I sure as hell wasn't going to be riding on the back!!! Your rear end starts to hurt and your knees get all tight.... how enjoyable is that for any extended duration of time? I guess everyone has their own reasons, but mine are plain and simple!!! 
Funny how this subject jumped out at me this morning. A woman club member was over here last night for dinner with wife and I. She is an Iron Butt (no, not THAT kind) Rider for the past few years. One of a very few that does these rides on a '06 RK. Remember, most of those people ride Gold Wings/BMW!!
We also have a couple of women in the club who have done some long rides, either solo or with a friend or two. On the other side, yes, we do have a couple "posers" who just want the "looks". I have seen them come and go over the years, mostly "go" when they move on to some other "activity" that feeds their ego. The ones who stay, ride and have fun, and are not too worried about "BUTTERY SMOOTH LEATHER" are a "class act" IMHO.
Oh yeah, if any of you members read this, (you know who you are!) remember, I still love you!