I don't have a problem with a couple meeting the first day, getting married, and having sex that very same night. The problem is the lack of commitment. If they don't take marriage seriously, they shouldn't have the ceremony. But taking a wife then not having sex doesn't resolve the ethical issue, IMO. And if they do marry, they take on a moral obligation to render 'due benevolence' to one another. But I think the show just shows a problem-- amplified a bit-- that is typical of our culture. A lot of people go into marriage with the idea that the marriage is disposable if things 'do not work out.'
On the show, they said traditional couples date first, then marry, and usually have sex on the wedding night, but this not a traditional marriage. I heard that and thought in a lot of cultures, especially historically, the bride and groom may not have even known each other well, or even at all, before the wedding. There was still the expectation of wedding night sex. For royals in Europe, the bishop and members of the court may have escorted them to the bed chamber with a bit of ceremony.
In the link I posted earlier about the clergyman on the show, he said producers approached his older son about setting him up on the show. He said he wouldn't mind if he were the one who got to set his son up, and he said he would trust the current experts. I sure wouldn't, but I can understand him trusting himself to do so. If parents were involved in choosing a spouse, it would be less crazy.
That bothers me, too. The guy who had the baby mamma kept talking about people praying for him, wanted his wife to lead him in a Bible study, etc. The one young pastor who was apparently a long-time friend tried to persuade him of the importance of keeping the marriage covenant, the one 'character' on the show who seemed to take this very seriously aside from maybe the bride of the man with the baby momma.
I don't think they legally get married, either, like in the US show. The Australian show seemed trashier from the clips I saw.