More than just an adult skill, good communication is a life skill. The ability to communicate is crucial, to be able to speak, read, write, work to understand others and the skill to process information, are not simply innate skills. Communication skills are learned and can be improved. Listening skills, negotiation skills and the ability to give and accept criticism as well as other rhetoric skills can benefit you all your life. Communication is one part of social skills. Social skills often aren't explicitly taught. Learning the basics of how to interact constructively with each other is incredibly valuable.
Part of adulting is learning how to turn arguments into a productive and enjoyable conversation rather than a bad-natured confrontation.
Another part of adulting learning how to talk to people when terrible things happen, when people get really sick or when people die, it is difficult to talk about, but important.