From my experience, even in a relationship with very high leverage (an employer working with an employee), it is practically impossible to motivate somebody to work on any relative deficits, even if the rewards would be considerable.
Self-satisfaction is a primary human trait.
To a first approximation, in a western democracy, the best we can do is corral and socialize humans until the age of 16 (sometimes the age of 20), and hope they pick up the habit of motivating and improving themselves. If that doesn't happen, then corral them for 50 more years, in institutions differentiated by the tiny amount of liberty they allow.
Comment prompted by Arnold Kling in Econlog: Goldin and Katz and Education Policy Failings in Historical Perspective