I like this explanation I’ve read somewhere about why it’s wrong to “test-drive” a person before marrying him/her: Marriage is not a consumer product that you give a try to see how it suits you. Marriage is a leaving of all other relationships to give yourself completely to your beloved. Cohabitation says, “I’m not sure about you. Can I give you test-drive to see what I think?” Melts your hearts doesn’t it, ladies? Marriage says, “I want all of you and I want to give all of myself to you!” This is why cohabitation and marriage are such very different kinds of relationships. It is why the social sciences have come to the conclusions they have about living together before marriage being a poor and unhealthy idea.
As for the one commenter here who claims that a “new survey” has refuted the other studies showing the negative consequences of cohabitation, I checked your link and it led to another link (still no reliable study), and then it led to another link (and still nothing there). I find that this “new survey” you’re talking about is not really reliable and is not even based on the scientific method! Sorry but your “new survey” did not really refute the dozens of existing SCIENTIFIC studies on cohabitation. Try again.