My wife was Methodist, I was Catholic. We were married outside the church and then after four years, my wife decided to convert (after stating when I proposed that she'd never become a Catholic). At that point, we had to go through pre-marriage stuff, which was funny, because we had been married for four years and she was pregnant with our second kid at the time. We've been married for 31 years now.
In response to the OP's original comment, the marriage prep may seem odd, but the Catholic church has been facing 50% divorce rates like everyone else. They are trying to prepare people more for marriage, and in some cases, maybe recommend a couple rethink their decision if they come off as totally incompatible. But all that prep is only as good as the couple and priest take it seriously, and of course, every couple thinks, "Love conquers all, and all of these differences will work themselves out!"
In response to the OP's original comment, the marriage prep may seem odd, but the Catholic church has been facing 50% divorce rates like everyone else. They are trying to prepare people more for marriage, and in some cases, maybe recommend a couple rethink their decision if they come off as totally incompatible. But all that prep is only as good as the couple and priest take it seriously, and of course, every couple thinks, "Love conquers all, and all of these differences will work themselves out!"