From: Eivind Kjørstad, on Quora (edited)
Rising divorce-rates in the modern world don't reflect a decline in marital happiness. There have always been happy and unhappy marriages. The difference between past and present lies in what people do when they find themselves in an unhappy marriage.
In some cultures, it's socially unacceptable to get a divorce. Also, if a woman is a housewife she might have little hope of providing for her family on her own. In these circumstances, few seek a divorce. Instead, marriages endure which are without passion, love or even friendship. Sometimes even without basic respect. One of my Iranian friends has parents who try to avoid being in the same room together. Such a couple would almost certainly divorce in a culture where it was more acceptable.
In modern countries, it is common for married people to divorce when neither partner is abusive or unfaithful and sometimes even when there is still a functional friendship - because one or both feel that the marriage is no longer providing what they want.
And, one should not consider divorce a failure. If two people live together happily for 3, 5 or 10 years but not for life, why is that a failure?