I don't want to spank you. I don't need to. You've done nothing wrong of which I'm aware. Why should I? What's my motivation here? Give me one good reason.
The ONLY reason I can conjure is that I just want to feel the soft skin of your naked ass cheeks. It doesn't have to be sexual in nature. I can use various scented oils or lotions. The longer it takes for me to rub it into your skin, the better I like it. I like to follow the shape, the curves, the crevice and your upper thighs.
I don't need to look at your face. I know your eyes are blue. I remember your lips of dark cherry red. I love the face behind those things. I love the person behind all those things. (pun intended) Right now, I just want to rub your ass cheeks.
Okay, you can be naked if you prefer. I like the soft feel of those lacy panties you have. I know they were expensive, which only adds to the visual appeal -- as designers intended.