As per subject why is this? According to the meaning of the word Lucifer from other languages which are not english, Lucifer would derive from Lux in Latin, Luce for in Italian or Luz in Spanish which actually means light or the one that brings light. Associating light to good and darkness to bad (or sins) by logic, the term lucifer is not appropriate for how the element is described in the sacred scriptures.
Recapping, the theory wants that Lucifer would mean Thy who brings light. Why is a being/daemon/entity/angel etc which in theory is nasty and bad be called the one who brings light?