It is impossible to answer your question for those couples you had that experience with but never told you their reasons. The only thing people in here can do is assume.
Here are just a few possible reasons that come to my mind:
* Like
@just_jenna said, the wife could possibly have caught feelings for you that are exceeding those of "just lust".
* It was never the couple's intention in the first place to meet a guy more often than once.
* Some jealousy issue on behalf of the husband's part.
* You spontaneously did or said something that was a red flag to both or one of them.
* They'd decided to give it a try even though your terms did not exactly match their own prefered play scenario and found out the experience was not that pleasant to them as a couple (even the wife had her o's).
Also consider the following: Couples in
this type of sexual lifestyle prefer a man as the third player who understands
their lifestyle well. Of course there are couples willing to share with nothing more than the sex in mind. But many couples are looking for more than just the sex. Some want to make an experience and create a memory for them as a couple, and have the husband included/involved in ways that suit
their dynamic best.
You can play with a wife but in a consensual sharing situation in which the husband knows and supports his wife's playing with others you are always involved with the couple, never the wife alone even if you meet - just the two of you - in say, a motel room. - The husband is always involved in one way or another.