"Living in sin".
That's what cohabitation before marriage used to be called. It was only those willing to risk social stigma and rejection who would dare to live with their partner before marriage or without any intention of getting married. It's not that many years ago that such a lifestyle produced social criticism and condemnation.
Today, cohabitation before or without any intention to marry seems to be not only acceptable but, in many quarters, is expected and even encourage. I don't know the statistics for Australia but a recent "US News and World Report" article stated that more than half of the newlyweds in the USA lived together before tying the knot.
Interestingly, that same article quoted research indicating that, among unmarried cohabitors, there was significantly greater domestic violence, depression and cheating on each other. In fact, some sociologists doing research in this area are now urging young adults to reject the argument that cohabitation is good preparation for marriage.
None of these findings ought to surprise us. The bottom line is that, if marriage is God's idea, then ignoring the Maker's Instruction must inevitably and ultimately lead to a malfunction of the "product" – in this case, marriage. And please don't tell me that a piece of paper (marriage certificate) makes no difference. I already know that. What does make the difference is the lifelong commitment represented by that piece of paper.
As one who has counselled a lot of couples over the years – pre-marriage and post-marriage – I have had a lot of opportunities to observe and interact with many different philosophies and perspectives to do with marriage. The happiest people I know are those who are committed to each other and who are committed to follow the Maker's instructions.
That doesn't mean that everything in life for them is problem free or without struggles and tensions. What it means is that the couple who are committed to a lifelong relationship as per their Maker's instructions have a framework of loving security that enables them to stand together as they face the problems and tensions that are part of life's experience for everyone.
Frankly, I don't understand why any couple would want to settle for anything less than that.