I don't think it has to all be about sex, but for me it pretty much is. I already have a loving caring relationship with my husband and daughter. I put them and their happiness/needs before mine alot, because it makes me feel good. But do I "have to"? No. I feel like this position in a d/s relationship is more expected and i know I would feel more like I had no choice. It's giving that power to someone else that happens to be a turn on to me sexually. It's where this subject fits into my life and meets needs that I can't get any other way.