This article points out a pretty important obstruction to the general spread of rationality:

So what were the key differences [between the slow spread of antiseptics and the fast spread of anesthesia]? First, one combatted a visible and immediate problem (pain); the other combatted an invisible problem (germs) whose effects wouldn’t be manifest until well after the operation.

Rationality training does not combat a visible and immediate problem because people do not have a sense that more is possible along this dimension.