In your opinion, why do women enjoy being spanked?

I get the whole dominant/submissive dynamic that most women enjoy during sex (e.g. the male partner holding the woman down and having his way with her).

But what is the sexual appeal of being spanked? Spanking is often done to reprimand or punish a child for inappropriate behavior. So how does a traditional act of punishment translate to something so enjoyable in the bedroom?

Do some women act like they enjoy it just because they know their partner is fond of doing it?

Personally, I have been with women who have openly requested to be spanked which makes me question the above hypothesis.

Is it often the byproduct of an estranged relationship with their father or stepfather? The reason why I suggest this is because of the old saying that women with "daddy issues" are often the most wild in bed.

Also, I've noticed that heavier girls seem the most likely to prefer the act of spanking. Why is that so?

I'm sure there have been a few psychological studies conducted to understand the female psyche during sex, but I wanted to get the average individual's opinion. Thoughts?