Board Thread:Fourth Databook/@comment-24577388-20141105025614/@comment-2120712-20141105063131

Probably because as the shinobi learns more they come to realize that learning all 7 elements is a inefficient waist of time unless they know where they want to go with each one of them. Sometimes being a jack of all trades is not a good thing. You need to be excellent in something. Look at the last two Raikage. Learned many elements but rather than stretch their potential to mediocre, they focused on one of those elements and became masters of said element with one even taking lightning release to a new form. My guess is that those who can learn all 7 elements and master each one to a high level are rare, as learning how to make a certain elemen.t is just the first step in a life time of study and mastery of it