As it should be. It is between two people and God. It’s only fuel for gossipers inside the church. Who needs a sermon on divorce? Both or at least one is more than likely devastated by it. A preacher should not waste the time of a whole congregation to preach/teach on divorce when no one wants divorce but some do ‘want out’ and they/or one goes privately to the pastor for counseling.
I don't agree with you here. If all the pastors thundered from their pulpits "God hates divorce" (Malachi) as much as they preach against other things they are against, abortion, same sex marriage, etc., there would not be nearly as much likely hood of their church people running off to get a divorce for the slightest reason, bored with their spouse, etc., or as Matt. 19:3 puts it, "for every cause." A lot is going to laid at the feet of preachers for not preaching against divorce.
Preachers don't have a problem bucking the trend when it comes to abortion and same sex marriage, but they, for the most part, don't want to buck the "divorce for every cause" (no fault) trend.
There is a reason society in general in Christian America in the 19th and for the first half of the 20th centuries, had very little divorce. Preachers everywhere, and their congregations since most went to church back then, preached against it, society in general knew God was against it.