As a teen with a developmental disability becomes an adult, the deficits in their social behaviour would become more apparent and have more of an impact on their daily functioning.
For example, imagine an adult with a supervisory role in the local supermarket who had a social behaviour deficit. They would have staff that they would need to issue instructions to in order to have food placed on the right shelves, in the right places. Without the skill to be able to ask that of their colleagues, the supervisor may end up doing it all themselves rather than interacting socially with the staff around them.
Alternatively, consider the other skills we have discussed this month; the listener and echoic skills, and imagine that a young adult is out at a party for the first time. They would need to use each of these skills to help them function well at the party. Firstly, they would have to listen to the conversations around them, if they were unsure what to say they could imitate some of the language of the peers around them. We use these skills so that we can be in relationship with other people, and so that we can function well and fit in.