Eye contact is necessary for communication and bonding. It can also be done with the environment and objects used for a task, and other people will pick up on what you’re looking at. Proper eye contact requires good visual attention, see for example here, or this post on eye contact and attraction.
Eye contact is the main form of communication with babies. It creates a secure attachment between the baby and its parents and thus fosters its development. Vision in interrelation with the other senses allows the baby to discover and explore its environment. It also helps to confirm the information received by the other senses.
For children, eye contact plays an important role. It saves the information provided by the caller or mimic the behavior of adults to learn how to do an activity or just to play. Eye contact is essential to develop social skills and motor skills, and prolonged eye contact can signal attraction. At the school level, eye contact is used to read and make connections.
The lack of eye contact with people or objects can make it difficult social development and the development of motor skills, because the child is not sensitive to feedback from the environment perceived by the eyes. This is also a common problem with autistic children. More broadly, visual problems may also delay language learning in addition to causing difficulties with spatial relations (above, below, etc..). These difficulties can be associated with several health conditions including cerebral palsy, autism and delay delay.