[jessriedel]

All science is about belief. Randomized controlled trials are useful not because they convey mathematical proof, but because they give strong evidence for beliefs.

Your question doesn't help. For the sake of argument we have granted that marriage causes men to earn more money. And yet, I would still prefer to marry someone who was earning more money (or who had the potential to earn more in the future), all else being equal. This preference doesn't dispute the causation.