It's understandable to frame it in this way, and there are legitimate predators who take advantage of people in those environments. The common case is more pros

It's understandable to frame it in this way, and there are legitimate predators who take advantage of people in those environments. The common case is more prosaic: addicts are often codependent and will seek romantic companionship amongst each other, especially in close personal environments like that. Starting a relationship early on in the recovery process is a common (yet tempting) mistake and conventional wisdom warns against it, which is why the phrase exists. [I spent a few years in the orbit of 12 step programs in my youth]