What causes interest in SB?

I’m wondering what causes this for certain folks. Back when I was young, bondage was already on my mind. No one brought it up or recommended it to me. Meanwhile, the girlfriends and two wives I’ve had didn’t care for it and thought I was nuts. There must be some psychological factor at play here. As they say, those who were spanked frequently as children tend to enjoy spanking in adulthood. I never experienced much tying or spanking growing up, yet I do appreciate both bondage and spanking now. Does anyone have thoughts on why this occurs?