A rich man doesn't have to tell people he's rich. Its evident in his demeanor, his dress, his outward presence, without him having to broadcast it. The first thing one thinks of when they encounter an overly religious person making grand displays of proselytizing is the the guy's a phony and a hypocrite. Likewise a "happy couple" doesn't need to wear their happiness on their sleeves.
The happiest couples you know - the ones who are the best fit for each other - are the ones who display it the least. When I hear a husband continually pop off about how lucky he was to get with his wife because he's such a hopeless schmuck, or I see a woman post "for the both of them" on their communal Face Book profile, it tells me all I need to know about their relationship. It's struggle, it's doubt, it's a constant need for convincing themselves that what they're doing, who they chose to commit their lives to, how they need to "work at their marriage" in order to keep it fresh, is all according to some greater design.
Good couples don't give this a passing thought. People love to tell that a good relationship is hard work, bullsh!t. A good relationship is effortless; it's matter of fact, not a constant role one plays or an advertisment.