In the cult I was raised in, many feel obliged to get married young, considering that any sex is forbidden before marriage and that flirting too is taboo. Flirting is only allowed "in the optic of marriage" and the couple should be accompanied so they're never alone. In reality, life is more complex. This also means that there are many divorces. How could it be different, if they barely knew eachother before "engaging for life"? Then in practice, many teens and young adults in that cult fear penetration deadly, but practice other forms of sex, like dry humping.
It is more realistic to date and see how it goes, if it should eventually evolve to wedding, etc. Of course, there are cases where they also get married because of a pregnancy, trying to hide the fact that they violated the church's rules. Because the demands on people are unrealistic, the violations are unevitable.
At least where I live, most Catholics of today tell me that it was similar for their grandparents, but these are in the more realistic camp. Some latin people I know told me that out there it's similar to how it was in the 1940s here.
In my case, despite a long term relationship there's no marriage yet. Maybe someday. I almost got married when much younger and it would have been a bad idea back then, I'm glad I didn't. I actually lost track of the person, unlike with various friends of the epoch.
In any case, in love like in many things, people have their ideals and expectations that are more or less realistic and met. There are happy and unhappy marriages, some where they should have separated long ago but didn't, others that were and came back together, etc. At least when the choice is there it's possible to try to make it better next time.
My own parents were never happy in marriage. Both told me they got married too young, that they stayed together out of necessity for children before, then out of necessity for church reputation after. My dad's church reputation was lost when they separated later in life (in that patriarchy, men can have congregation "privileges", but they are lost if they don't "lead their family exemplary", a separated wife means they've lost total control). In my impression, they should ideally have allowed themselves to date other people, but apparently didn't.
And for many, there was passion at first, it may mostly have been romantic and sexual, but there's more in life to it, so the perspective changes. Then people get older, libido is affected, the aspects of attraction and love will express differently.
That's just life. Why make it more complicated than it already is with unrealistic rules enforced by third parties? Dissent against that type of authoritarianism is noble.