Answer: Because it has nothing to do with physical life. The soul is what we invest in others, when we are found with them and feel our eternal state through them, still in this world, in this life, in this body.
The structure of the soul is composed of ten Sefirot. We must know how to assemble and give life to this system so that all parts of the soul will complement each other mutually. For example, if ten people gather together and want to create mutual relationships like these, they can dissolve into each other, and each one of them can go out of himself and not remain a little egoist.
When I go out of myself into my nine friends and each one of them does this too, a network of connections is organized between us and we begin to feel that we are within it.This is the feeling of crossing the Machsom (barrier). Within me I am an egoist, but when I am included within them, I am an altruist, and then the common desire and intention that we create between us is called the soul.
The network of our mutual relationships with the characteristic of bestowal is called the “Kli of the soul,” and the particular form of the upper Light that is revealed within it is called the Creator.
From the Kabbalah Lesson in Russian 11/1/15