Why do all these celebrity couples look happy?

Seriously, in the media, magazines and even interviews on Jimmy Fallon or Jimmy Kimmel, whenever a famous person talks about their marriage, they act like their lives are all peachy and there's no problem at all (I know celebrities are just human, and I can't stand the way the press treats them). I was recently watching an interview with Alison Brie (who id love to meet) talking about her husband Dave Franco and she acts like her life is "sunshine, lollipops and rainbows". Come to think of it, how do some famous couples keep their marriage long-lasting? Ie Kevin Kline and Phoebe Cates, as well as Freddie Prince Jr and Sarah Michelle Gellar.
Why do all these celebrity couples look happy?
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