Well, actually some may know the answer to your question. In a nutshell, it's because of the original sin of the human beings, which is the very ancient rebellions against God long long time ago of the (now physical) human beings, as angels back then, on other spiritual worlds, in a different dimension than this physical one.

After these rebellions happened, the beings (back then as angels) were forewarned about the terrible consequences they would suffer and asked to repent and accept God's punishment, but that didn't happen, so God decided to expel them (us) from those spiritual worlds and punish them in these harsh physical universes for a very long time.

The basic of all basics of these physical universes is the huge guilt that humans have, which gets carried on on each cycle of the reincarnations, until God decides that enough is enough.

There's some actual truth to the 1667 poem "Paradise Lost" by John Milton, which specifically talks about the luciferian rebellion.

P.S. If you (or any other) have questions, feel free to ask. I'll try my best.