A source of communicative inefficiency is

A source of communicative inefficiency is limited knowledge.

When the communicator knows too little about the subject or the audience, the message weakens.

A desire for personal gratification is a motive, not in itself a cause of inefficient communication.

The implications of familiar relations can even ease communication rather than break it.

Peer pressure affects choices but is not a core source of communicative inefficiency here.

Filling the gaps in knowledge is what makes communication more efficient.