"Couples" puts everybody in involuntary performance mode. It starts super harmless, the "and" element (the side in a couple that came along) having a natural desire to be good with the friends of their partner (the "and" side is prone to greatly overestimate the depth of the relationship that lead to the invite!), the other side (the one that had the "link") trying to make their partner feel good with that group. So far so good, everybody does the reasonable thing, sounds super nice. But that very same thing happens within every couple, nobody in the room who isn't in "prove myself to my partner" mode. Before you know it escalates into a take-no-prisoners battle of showing off which couple functions best. It's certainly possible with couples despite all this, but there is infinitely more that could go wrong along the way.