I'm still very new to this type of (admitted) relationship. I believe I've always craved this dynamic, but couldn't name it, and could never bring myself to ask for it, so it mostly found expression in sex.
I'm still in analysis stage, and putting together what I think may be reasons, but my love of the missionary position was my first inkling of these feelings, having the man on top, and not feeling demeaned, but protected and safe, with him very close, and able to shield me from things, hold me, etc. I liked the intimacy of being able to whisper in his ear some yummy naughtiness.
Feeling his strength, his masculinity is a huge part of the experience, it's like he's strong for a reason, because I need him to be, because I need him, and it's a tremendous turn on.
I know, women aren't supposed to want protection, we're supposed to want to go out and wrestle problems to the ground, but I've done that a lot, and had to deny a lot of my softness to make it possible.
Hopefully in reading this site, I'll be able to reconcile my urges, upbringing, and personality, but for now I'm having a great time reading the stories.