Because history teaches us that people in genuinely happy families, doing good things for others, don't constantly need to make it public knowledge, they just get on with it.
Those who have an ongoing campaign of cultivating 'happy family' photo albums for the public are putting a lot of effort into prioritising appearances - including a carefully curated range of messy/drunk shots - which is the first sign of something being less then genuine, especially if you've got a celebrity lifestyle and range of products to sell.
Back in the old days, you had Cindy Crawford taking out a full page ad to tell the world her marriage to Richard Gere was wonderful. These days, celebrities can spam the world with their chosen message through social media. What doesn't change is how the real picture comes out in time.
I wish them well - I just don't buy what they're trying to sell me, and I especially don't like how they think I'm stupid enough to eat it up.