All these terms are fascinating.
Therapists, counselors, and relationship experts do not view cohabitating boyfriend/girlfriend as having a relationship but a "situationship".
A situationship can have all the appearance and perks of a relationship but without the commitment, obligations, and expectations of a real romantic partner.
Those who have been in a situationship, especially if they've been in more than one, are more likely to have a higher divorce rate should they get married. Whether that is to the situationship partner or to a new person.
Situationships do not help the parties involved to develop healthy patterns of relationship behavior. In fact, it is the opposite, according to therapist Suzanne Venker. Why? Because a situationship sets up the parties involved how to find the negatives and red flags in their partner in order to justify ending the connection. In other words, these people get together to break up. Think of it this way, "let's live together and act like husband and wife, so that we can find out if I really want to marry you." Well of course you would only be looking for the negatives.
And once they identify the negatives, there is no obligation to reconcile when the entire purpose was to look for red flags so that you can exit. Whereas in a marriage, you are there to reconcile and work together through the red flags. Each partner is more willing to work through challenges in order to keep the marriage.
Situationships teach the parties involved how to perfect a breakup. They're used to it and view it as a good option - in fact, the only solution to conflict.
Those who have been in one or more situationship have a more pessimistic view about marriage and are least likely to enter one. I'm not saying that marriage is the only kind of connection to have. If two consenting adults are okay with a situationship then by all means, do whatever floats their boat. But just know that the situationship has a guaranteed ending - it's kind of the purpose. You're only in it for as long as it is convenient and enjoyable.
However, the ending of a situationship doesn't come without grief, heartbreak, disappointment, and trauma. In fact, some might say it is more traumatizing than a divorce. With a divorce, the parties involved can at least say that they gave it their best shot. They don't have to wonder the what ifs, and they don't feel taken advantage of. Something that cannot be said about a situationship. One party, particularly the woman, always feel like she was used and misled. Because the woman tends to invest more emotionally, often times financially as well, in a situationship since she is hoping that it would turn into a full commitment. And she feels pressured to prove herself as good enough for him to commit to. Unless of course this is a dynamic where she is a gold-digger, then the man will feel a lot of anger when it ends.
Also, people who were in a situationship carry their negative experience and developed bad behaviors into the next relationship. They project all their insecurities and pessimism onto the new person. The same reasons that people hesitate to marry a divorced person can be true for why someone would hesitate to get with a person who was in a situationship. Again, a situationship may not have involved full commitment, but it certainly included many of the perks and pitfalls of a marriage. And again, I always say worse since parties in a situationship never fully gave themselves so they're not even conditioned to know how to behave like a fully committed romantic partner.
Therapists are finding that the majority of their clients are those who were in a situationship rather than a marriage. Modern dating and feminism have moved the culture away from marriage and more people are getting into a situationship. Therapists are saying that this has changed the way they practice because those suffering from a situationship breakup are having a more difficult time healing. Furthermore, they get into another situationship or find themselves divorced when they marry. This is why we're seeing a dramatic increase in divorce rates. It's not just divorced people remarrying and divorced. It includes never-been married people whose had a situationship that don't know how to cultivate a healthy marriage.