Only I don't think that's quite true.
The kind of motivation you need to work at the same thing, day after day, can be fueled by many things—and not all of them are as positive as iron will. Profound emotional damage, for example, will do just fine, as it's a constant push to lose yourself in work. Desperate, gnawing lack of self-worth is another common one, since it can be temporarily beaten back by personal accomplishments.
And let's not forget OCD. Nothing makes you perfect your craft like the inexplicable feeling that you have to.
So maybe the reason most people goof off so much is that they're relatively well adjusted. The person who's happy, healthy, and fulfilled doesn't need to conquer the world.*
*They just need to pretend to.