Even if you don’t ride 2-up chances are if you ride with others, or are inclined to help someone in need, you may end up having to put someone on the back off your bike at some point. Maybe while riding off-road with friends, someone’s bike breaks down and they need a ride out to get help. If you have the skills, you suddenly become a rescuer, if you don’t have those skills, well - it’s a different scenario all together.