It helps young children/babies control their emotions.

It strengthens the bond between a parent and child, as a child's needs are better met and communicated.

It helps kids with developmental disabilities communicate easier

It sometimes helps kids start to use their words and speak faster

There is a reduced number of tantrums and outbursts from the baby

It helps kids develop their cognitive abilities as they use their hands to communicate

It has the possibility to help kids communicate with sign later in life as well

It helps young children connect better with other family members as well

It can be used anywhere from at meal time to during play time so a baby and parent are better able to understand each other's ideas in many different circumstances

Relieves anxiety for the baby because they are better able to communicate their needs

Source: https://www.canr.msu.edu/news/baby_sign_language_a_helpful_communication_tool