Much as I love my Lady Wife, I have asked her more than once if she would like to be involved in the Club and/or come out on the back of the Bike and her flat answer was No. For the simple reason that she is really not interested in Bikes of any shape, size or colour, and treats the ST as strictly my hobby, as sewing, knitting and crochet are hers. She cannot understand why I would need to have her involved in my riding, nor can she think of anything that would actually interest her in being on the back of a Bike.
Now I fervently believe that ladies (and any other pillion riders) can find overwhelming interest in being on the back of a bike, but only for those who actually find this type of pastime fascinating. For those who are not inclined that way, the concept of thundering around the roads in a position that they can't actually see much from (and this seems to be the case for most women... I'm 188cm, my wife is about 155cm, so she can't actually see the world ahead) must be viewed as both fairly pointless and somewhat frightening. It can be cold, wet and dismal, and without the overwhelming interest in actually controlling the bike...i.e. riding, it must be both scary and boring for those not interested in the process.
Someone once described riding a motorbike to me as "...long periods of boredom, punctuated by moments of sheer panic" and whilst I don't necessarily agree with the "boredom" bit, the "sheer panic" bit certainly applies!!, so if my lovely lady wife can't see a reason to plant her rump on the back seat then I see no reason for trying to make her.
My personal opinion entirely, but strongly supported by She Who Must Be Obeyed!!!