The last time I had a pillion, it was a lady my friend's wife invited on a ride with us. I was on a Heritage, and we rode over 300 miles with one brief stop. I had to peel her off the back and hold her up as her legs had stopped working. I said "never again", and haven't had anyone but my son on the back, a few times.
Most important to me is not being responsible for another's safety and well being, when I cannot control how they react to turns, breaking, accelerating, etc, while on the back of my motorcycle... My ex was a good passenger, except for the bitching about weather conditions....