Isn't just because we've already been trained on that since learning the alphabet? Imagine giving a human the same question, but sort "aa" before "bb" but after "cc".
Maybe it's "just" because of previous training, but it's still a very useful ability, which programs do not have.
Being able to solve quickly the most common cases (which rely in such "common knowledge") would automate a lot of work that now requires writing a complex program in advance, and would allow the user to concentrate on the outliers that require more thought.
