Even supposing that were true, it's arbitrary to place fallible biological systems of motivation and reward into the "personal problem" category, as if they were not part of the same overall biological system.
If a computer program crashes would you investigate the problem by opening the case and testing the chips inside with a voltmeter? My motivation in labelling the problem as I did is to show where I think it truly lies and thus make it easier to solve. Metabolism is notoriously complicated.