Why do we use pronouns?

A pronoun is used to take the place of a noun in a sentence. Pronouns perform the same functions in a sentence as nouns; as the subject of a sentence or clause and the object of a verb or a preposition.

We use pronouns so that we don't have to repeat the same noun every time we refer to it. Pronouns help sentences flow more smoothly.

Example:
Mary and John bought a new house. Mary and John have asked for volunteers to help paint Mary and John's new house.

OR, using pronouns:
Mary and John bought a new house. They have asked for volunteers to help paint their new house.

Example:
Andrew left Andrew's house early because Andrew was excited about the excursion at Andrew'sschool that day.

OR, using pronouns:
Andrew left his house early because he was excited about the excursion at his school that day.