This question (the one the thread is all about) comes up a lot. For me, anyway, I switch because I want to be able to experience the full range of erotic possibilities. I enjoy sexual power exchange in too many and varied ways to want to be limited to one role only. The saying used to be "your kink is ok." Well, my kink tends not to stay put. I'm ok with that, whether others are or not, but it does complicate finding the "right" partner to be with.