I've been the outside man for couples (by now many many dozens) since I was a teenager. Mostly the husbands/bfs have watched at least some of our sessions. Almost always, I was there because the wife wanted more pleasure and satisfaction than her man could give her. The size, thickness and foreskin of my cock almost always was part of why I was invited (in addition to power, skill and experience, over the years). So I am almost always superior to the hub/bf sexually and make the wife orgasm far more often and more intensely than he ever had, as well as given her sensations that he never could. This often leads the wife to disregard her hub, forget about him in the intensity of our sex. Just last weekend the guy couldn't stop telling the wife what to do, and she had to ask him to go outside until he could shut up. They both loved it anyway.
These days the husbands are usually totally on board. When I was younger, I would sometimes get into situations where the hub or bf would become jealous, hurt or depressed at the wife's reaction to me. After all, it's hard to be left behind that way. It led to a few angry or crying scenes, where the guy couldn't deal with his wife's sexuality, as beautiful as it was. I learned to finesse myself out of these problem sessions. Usually the couple would talk it over, the hub would be reassured and they would come back. Sometimes I learned there were bad consequences.
As I got more experienced, I learned how to avoid these problem feelings all together. These days, I can help the hub adjust, or get out of a bad situation before it starts.