>>289578501. Degradation is hot. The idea that my girl is a big enough slut that she is that desperate to please me is a huge power trip. My current fiance is also my submissive and she's a germaphobe. It took a while to train her to want to do this to me and now it makes her wet so its a nice preamble before sex.
2. It feels very good, its a pleasant tickle and you can grab your partner's face and really make them lick your ass, balls, and cock. It's a combination of physical and mental pleasure.