That's not true in my experience. I've been partner dancing for about 6 years and that's where I met my girlfriend of the past 5 years. We still dance every chance we get (we have a portable dance floor in our apartment). It's absolutely wonderful that we have something that we can learn and excel at together.

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.