There's another reason why the Pattersons don't like to hear their children complaining about their lot in life; as we've seen, John and Elly share with Lynn the habit of respecting people who suffer horrible things in silence. The catch-phrase they use is "Complaining is good for the soul unless you're complaining to the person you're complaining about." This perversion of the ideal we are pleased to call grace under pressure does not, as one might hope, come from an admiration of their idol's bravery; it stems, as we know and loathe, from their need to not be burdened with the concerns of others. Since the Foobs think like the spoiled children they are, they interpret having to worry about someone else as having been beaten at some sort of martyrdom contest by said picky-face. Let's, as a for-instance, assume that John and Elly had to take Lizzie's concerns about Mike teasing her seriously instead of shrugging and insisting "siblings-fight-it's-the-way-things-are"
like they want to; what that would mean to them is that instead of having to worry about how Phil always got treated better or how Carrie seemed to wear the pants in the family, John and Elly would be forced to worry about their children. They would interpret THAT as having the children setting the agenda; the loss of face they'd think they'd endured would be devastating. It's better for them to get pissed off when their kids get all clingy because they think that if they "give in", the other parents will respect them less. This need to not be thought less of is also why they've never shown their children any sign that they actually get a kick out of the stuff they do; it's better for them to be seen as stern, unyielding authority figures than to be known to be human.