Board Thread:Theories and Speculation/@comment-5012682-20150620162706/@comment-25626003-20150620175449

That paper test determines what your true affinity is, and in Sasuke's case it's lightning despite being an Uchiha. He's a rarer breed indeed, but as JOA20 said, anyone can learn all five. It's just what's the point? In Sasuke's case, there's no reason for him to bother training in Wind, Earth, & Water when Fire & Lightning are far and away the most effective for him.