To further explain, Steve admits to being 'fascinated' with the story of Rick, (who's wife is exclusive to her lover) even though he say's he would not allow it to go that far. Many of the threads on this site describe the wife as very strong and controlling. I don't believe Sue would qualify for that roll.
There is another thread that asks the question why any man would be willing for other men to fuck his wife.
1. He feels inadequate, himself, and feels that he "owes" it to her to let her take fucks from other men who can do a better job then he.
2. He may be punishing her, for whatever reasons, by making a slut out of her.
3. He may feel guilty about some behavior of his own, like maybe fucking other women, and is trying to make it up to her.
4. He may have homosexual tendencies, and cannot bring himself to have sex with other males, so he offers his wife's body as a replacement and gets his needs for contact with other males satisfied that way.
5. He truly may love his wife to such an extent that he wants her to have as much sexual pleasure as possible, no matter what the source, and when he "allows" her to fuck with other men he is just doing her a favor.
6. Because it turns him on more than anything else
I believe Steve, from what he wants to feel and what he wants Sue to have, fits into #5 & #6 Mostly #6 and that is all he considers without considering the consequences.
Cheers, Harry