Watching your wife suck other people's dicks is a buzz kill. And she understands that by licking other people's testicles, her husband's boner will get sharper. So these swinger couples swap to sharpen their senses, bring back the novelty, and make their orgasms brighter. Only I would make the lighting not so bright, then there would be more understatement and less embarrassment.
What could a blonde be thinking about? Shopping, spas and sex. And if she's offered a black dick, she'll even forget about the first two things.