Perhaps that's true in general, but all I can say is that wasn't true in my case. I had several relationships after becoming fanatical about it, and never stopped dancing.
I have seen some people meet while learning to partner dance and quit, however. Not because they "bagged a good one" per se, but because some couples think that they're only allowed to dance together (which can get boring no matter how you slice it) and have a difficult time accommodating each other in the learning process.