Anna Salamon and I are confused. Both of us notice ourselves rationalizing on pretty much a daily basis and have to apply techniques like the Litany of Tarski pretty regularly. But in several of our test sessions for teaching rationality, a handful of people report never rationalizing and seem to have little clue what Tarski is for. They don't relate to any examples we give, whether fictitious or actual personal examples from our lives. Some of these people show signs of being rather high-level rationalists overall, although some don't.
Since rationalizations are usually employed to repair cognitive dissonance, and cognitive dissonance is strongest when image preservation is necessary, one hypothesis would simply be that these people have self-images that don't need much preserving.
Possible test: do these people have an unusually high tolerance for situations and/or self-disclosures that most people would find shameful, humiliating or embarrassing? This might explain a lack of need to rationalize, regardless of the reason for the high tolerance. (For example, we should expect sociopaths to not see any need to rationalize their actions to themselves.]
[Edit to add: not to imply that any of the people in your experiences are sociopaths; just noting that it's another situation where somebody would have a low need for self-image preserving rationalizations.)