All this. For a bad analogy, this is more the physics of game design than the practical mechanics. Can one benefit by examining this? Sure. But one can also go down some deep rabbit holes of some rather dedicated navel gazing and not come out with practical applications for one's own game design, be it for one's own table or for wider publication. Knowing what motivates "Players" doesn't mean as much as knowing what motivates "my players", but having some notion of these concepts can help on some level evaluating what "my players" want. Part of the issue is that it takes proper reflection for anyone to really know what they want. People often claim they want Bold flavored coffee, but statistically, people prefer mild. Are they lying? No, it is simply that Bold sounds better than Mild.