Doris, what drew people to watch J&K over the last few seasons effectively died last night. It started out chronicling the day-to-day lives of a "unique" family. Things started to plateau when it morphed into "watch the family get to do things for free your family likely never will". When news of the marital strife hit, the bloom fell off their "America's Sweethearts" / "Cute Family" crown and people started to get turned off. Sure, they set a viewership record when the season premiered last month... but then the ratings drove off the cliff. Last night's episode of "Pimp My Divorce" no doubt will be ratings gold, but the ratings free-fall well be back next week with a vengeance.
You're right that most American marriages end in divorce, but you're missing the key ingredient in "reality shows". The reason people watch them is because it features a look into something either that new would love to be able to do (i.e. "Top Chef") or offers a an experience very different from our own (i.e. "Little People", "J&K", "Duggars", "Housewives", etc.). Being an "average" family won't cut it in TV Land. TLC ain't gonna come calling to make a series out of my family or yours. So repositioning the show as "watch Kate deal with her loneliness", or "see if Jon marries the young teacher that won't keep his privates in a jar under the sink", or "what will Kate do with her week with the kids", or "watch J&K fight over the kids, money, etc." ain't gonna work. It's not entertaining to the masses, it would be pretty depressing, and for too many people it will remind them of their own lives. True, some people can't help but watch a train wreck as it tumbles to a stop, but it ain't gonna be enough to sustain the show.