When was the last time you were caught off guard learning about a couple splitting up? This happens to me pretty routinely. Does my radar need calibration?
Maybe so, although I suspect a simpler explanation is more plausible. Appearances notwithstanding, the only people who ever really know what's going on in a relationship are the people in that relationship. Are people who openly bicker headed for the trash heap? How happy are those couples who seem to rarely disagree? And what about those "storybook" romances the media regularly jams down our throats? If you and your partner could afford to pay a publicist - like say, Nancy & Ronald Reagan could - wouldn't your romance look like heaven on earth to everyone else?
It's not easy to avoid comparing your relationship to others. But each time another of those seemingly idyllic partnerships bites the dust - between people I know, i.e. those who can't afford publicists - the folly of drawing conclusions about who is happy and who isn't becomes a little clearer to me.