There are various reasons and purposes to why people communicate.
Some of the reason why people communicate are:
Reassure when someone is in shocked.
Understand the roles and responsibilities of others for example by communicating with a social worker, councillor ,foster carers or other organisations you will find out their responsibility they undertake.
To meet needs for example when a infant is crying the parents don't alway know why the baby is crying, finding out elimination, is he hungry, wet, tired, in need of burping, or sick.
Build relationship for example a teacher communicating with the children's to make them feel comfortable in their space.
Socialize It can mean just to mingle and discuss, Like we will socialize at the party. Or it can mean to change thru manipulation (guilt-trip) someone into conforming with others, supposedly the main of society thus you conform to so societal pressure you have become social zed.
Develop positive relationship with colleagues for example by helping each others and listening, respecting them.
One of the reasons is to find out information. For example, if someone is lost, they would ask another individual for direction. People do this so they are knowledgable on how to do something in a certain way.
Another reason is to understand each other feelings. People may want to understand someones feeling or mood or lifestyle. The way they would fulfil their purpose on wanting to understand a person is to communicate through asking questions about that person. This helps fulfil their understanding on that person.
Understand how roles and responsibilities affect others for example if your working in a childcare setting you should have knowledge of responsibility toward a special needs child and how their behaviour effect others.