Stigma against sharing your wife/gf

Only one of my wife's friends know we do this. We don't want anyone to know.
Kinda funny story....A younger couple we know, mid 40s, gooooooood looking, church going people. Turns out the husband was having an affair with the preachers wife for over a year. Wife was pissed off to say the least. Preacher wife tells the guys wife in hopes they all can swap. Evidently the preacher couple was into sex fun and swapping, preacher husband knew all along and let wife enjoy. First wife never cool with it, ratted them out, whole thing exploded.
Who knew