The words it, you, I, he and she are pronouns. They can be used to refer to objects or individuals. Further, from time to time, these pronouns are used to refer to different objects and different people. The meaning of each pronoun can last for just a short while, before the given meaning is forgotten or changed. Pronouns and nicknames provide short ways for talking and writing about objects and people.
Pronouns provide a form of shorthand.
There is only one pronoun it. For each object we meet or have met, we could say it. The word it is easily overused. The single pronoun it is not enough for us. We need more.