As I mentioned, the manifestation of what someone smarter than I am called the 'favor bank' system of morality is John and Elly's hateful, antisocial need to remind their children that they are somehow freeloading off of them because two self-centred and greedy idiots would rather not admit that Mike, Lizzie and April can't survive on their own until they're pretty much adults any more than they can admit that if they're going to create their own people, they have a duty of care that must be fulfilled without complaint. They owe society solid citizens instead of the freakish jerks they've blighted the world with.
This is because, as I've said before, the end result of their insisting on being paid back with interest is to burden the world with children deeply suspicious of true generosity. Mike cannot process the idea of simply being given something out of the goodness of his mother-in-law's heart and assumes that a wife with mother issues as crippling as his own is trying to cheat him somehow. After all, when he does do good things, he's told it either took too long or wasn't enough so Mira must be playing family politics lest his own family be regarded as being anything less than ideal.