A cargo cult is a particularly colorful way of mistaking cause for effect. Airplanes do not actually come to remote Pacific Islands because of rituals performed by soldiers at airports. But absent other information, to someone with no knowledge of the larger world, it might well look that way. So when the soldiers leave and the airplanes full of valuable stuff no longer come, it’s forgivable in its way that some islanders populated the abandoned tarmacs with wooden facsimile airplanes and tried to reenact the odd dances that used to precede the arrival of wonderful machines. It is forgivable, but it didn’t work. The actual causes of cargo service to remote Pacific Islands lay in hustle of industries vast oceans away and in the logistics of a bloody war, all of which were invisible to local spectators. Soldiers’ dances on the tarmac were an effect of the same causes, not an independent source of action...
The case for marriage promotion begins with some perfectly real correlations. Across a variety of measures — household income, self-reported life satisfaction, childrearing outcomes — married couples seem to do better than pairs of singles (and much better than single parents), particularly in populations towards the lower end of the socioeconomic ladder. So it is natural to imagine that, if somehow poor people could be persuaded to marry more, they too would enjoy those improvements in household income, life satisfaction, and childrearing. Let them eat wedding cake!
But neither wedding cake nor the marriages they celebrate cause observed “marriage premia” any more than dances on tarmacs caused airplanes to land on Melanesian islands. In fact, for the most part, the evidence we have suggests that marriage is an effect of other things that facilitate good social outcomes rather than a cause on its own.