There are two sets of reasons that make people getting married... or not. The first set, which I designate as "Cultural" relate to how people are grown up, what they beleive in and so on.

The second set or reasons, which I call "Rational", has more to do with legal and financial factors.

When the time comes for the big decision, each couple has to find its own balance, and this is not always easy...

The major cultural factors is obviously religion. Living with someone and having sex outside marriage is a fault and many get married because of it. No judgement from me here, it is simply a fact.

Familly influence is also important. If parents tell their childs that one must get married, they will. While raising a child, some concepts are burried so deep that they don't even question them later on.

Finally each one has a personal view on the important of marriage, and wants to satisfy it.

Strictly speaking none of these factors make marriage a must, in that sense that they won't prevent happiness and balance in the couple, as long as the community (familly, church, friends) accept it.

Many couples get married just before getting their first child, for simple legal reasons. It makes then no need for the father to legally "recognize" the child, and the proceeding in case of mother's death are much clearer.

Getting married also solves the heritage problems. Let's imagine a couple living together without being married, and one of them only has a job, providing money to both. Under certains country's law, if this one dies, all his / her possessions will go back to his / her parents, not to the other partner.

The same applies when it comes to getting a mortgage to buy a house. Most banks will consider married couples differently than a pair of single co-buyers, at least in Europe.

The legal / financial thing that prevent many couples to get married is the tax system. I don't know about the whole world, but in Switzerland married couples are much more heavily taxed than singles ! Because of that many get married only when the first child comes...

Please give any feed-back about these factors in comments !

I tried to list all factors that can lead to getting married or not. I do not want to discuss moral aspects, because this would be judging other people's personal values, and I don't want to enter this.

We all have to find our way, and our convictions are precisely that: ours.

I respect people who get married for religious as much as I respect those that do not get married for financial or legal factors, and vice-versa. As long as the decision satisfies both partners, there is nothing more to say. Respect it.