My (then) stoker and I were on our way home from a ride in Eugene, Oregon one fine summer day when we happened to blunder into gay/lesbian pride type of thing (such counterculture/ alternate lifestyle events being not at all uncommon in that particular venue, and mostly highly regarded by the populace, myself included). A pair of burley women accosted us and loudly asked "why is the woman always on the back?".
I appreciate and respect all lifestyle choices involving sexual orientation, but I was frankly taken aback and found myself at a loss for an explanation of such a clearly egregious behavior. I also later reflected that they were acting in the spirit of the moment with feminist fervor, high ideals, good faith, and so forth. As I have said, I, who am sometimes known for snotty rejoinders to such challenges, was speechless, and in retrospect was glad that I was.
What I should have gently explained in a spirit of solidarity was that, on tandems, the heavier, stronger person usually is found on the front. In the case of myself and my (then) stoker, it was definitely the case that I should occupy the front position if going by those particular criteria. However, it may have been a questionable matter had I been riding with either of these two worthy women, perhaps needing to be settled by the toss of a coin or a trip to the scales.
Let me add that Eugene is one of my favorite places to cycle in and around, with a large and active tandem contingent. It also rains a bit more than half the year, but is still a marvellous place.