Answer: Because the worlds are brighter (a smaller ego) and are weaker than the general desire that was created by the Creator. Each of these desires on the levels of 0,1, 2, 3, or 4 builds its system, which is made of five Partzufim on the background of the upper Light. Each Partzuf is made of five Sefirot, etc., and they make up concentric circles in which the soul exists.
Question: Is it possible to see the parallel worlds to our world in which the level of the still nature, the vegetative, and the animate were first created and only then man was created into this environment?
Answer: Yes. It is exactly the same thing. This is how man was created in the worlds and he also begins to develop according to a system of 0, 1, 2, 3, 4, the still, the vegetative, the animate, and the human levels of nature. When he completes his development the human nature is also divided into the same levels: 0, 1, 2, 3, and 4 and so on. This means that every part is divided in subparts and its own sub-levels.
Question: Does this means that these worlds are also desires, but simply are coarser?
Answer: They are desires of the still level. A pencil, for example, has a desire that comes down to preserving the shape and the attribute of its creator.
Question: Is there a pencil in the spiritual world?
Answer: Of course. It is a spiritual force by which man can write down his thoughts about his desire. A desire is the heart.
From the Kabbalah Lesson in Russian 5/14/17