Why is it important to consider your audience?
It is of extreme importance to consider your audience as you write.
If you are writing a nursery rhyme while using large vocabulary, what toddler is going to 1.) understand or 2.) have a long enough attention span to pay attention to something they don't understand?
Or visa versa
If you are writing a teen/adult novel and using simple sentences and writing as if you were writing to a child, the person would get annoyed and not want to continue reading.
Whatever the subject you are writing about, there is always a targeted audience that will most likely be reading your piece of work. If you take that into consideration, your skill level of writing should be spot on for whomever is reading it.
Also, considering your audience creates a greater possibility of readers, that understand what you are writing, and makes you a better writer.