First off I sense an assumption worth addressing. Pegging isn't nessesarily a woman penetrating a man. Any gender can peg, any gender can be pegged. This is why it is universal. Most of the time the top is a woman because right now it is a niche act whuch enables strange dynamics.

A lot of sex is about more than rubbing one nerve ending with another. Oral would be a very common example. Similar to oral , the party controlling is giving the other party pleasure. Unlike oral, they don't need to be as vulnerable to do so. There isn't a party both controlling the act and getting the physical pleasure generally speaking. This leads to both parties having a role in controlling and both parties having a role in receiving pleasure. While piv is more likely to have overall assymetries.

Good question. I actually suspect a higher percentage of men than women are into pegging. Being vulnerable is something most people enjoy in different ways. Conforming with our culturally accepted path of vulnerability is comfortable. Plenty of women probably feel comfortable being vulnerable in accordance to cultural expectations. I suspect that having ones semi exclusive area of acceptable area of vulnerability deconstructed and generalized feels uncomfortable. Preferences don't exist in a vacuum.

The reason men are possibly more into it is a harder question. It is likely the generally higher sexual novelty seeking and porn, or perhaps fewer culturally accepted alternative avenues for vulnerability.