This is a reasonably good question. There are a variety of ways that people have relationships and judge commitments. There is a variety of lifestyles available to people. There are special reactions people to have the marriage ceremonies – often due to social considerations about vows, and their significance.
The truth is that because people are different and society influences the events in our lives that it does matter whether or not people are married. However, the location, and many other attitudes are also involved. There are relationships which are are robust and loving and full of devotion without the need for what to some is merely a binding contract on paper – and you know that often people only need it in writing when there is a lack of trust….but for others is a sanctification. There are people who only respect romances that are marriages, or only when a religious marriage took place in a specific religion – the ritual has to be a certain one or they won’t even respect it.
There are relationships which are dedicated and stand all the tests normally reserved for marriages but legally, technically they are not. In some cases, this just makes the wife less financially or socially secure but in other cases it reduces the risk of people out to destroy their relationship because it is a marriage or worrying about whether support for the success of the relationship is broad or quite narrow.
Something to think about.