Answer: This is imperative because without learning the wisdom of Kabbalah, it is not possible to reach Lishma (for Her Name), which is what is necessary for everyone who studies Torah. The problem is the manner in which the concept of “Lishma” is interpreted.
It is customary to think that Lishma is already happening simply by studying the Torah. I have even heard that a number of Yeshiva students have reached Torah Lishma at the age of 20. So we must first clarify the precise definition of the concept of “Torah Lishma.” Regarding this, see The Introduction to the Study of the Ten Sefirot.