The reason they can't do better is that after speaking these words the subject is closed. Reward and finality has arrived. But how? You haven't said a thing. The world has stayed the same since the conversation began a few seconds ago. What has happened?
What's happened is all in the speaker's imagination, but no less real a social fact for that. In the speaker's imagination is a whole society of remembered conversations, and more importantly, remembered rewards and punishments for speaking certain words. Rewarding words. And the conversation is over when reward is issued.
So now you know. People who speak in key words, jargon, catch phrases, cant are the ultimate product of society, which means unfortunately not living in the society of the people they are with at the moment.
Surprised? Remember that words are products of the past, things people have made together in their past together. When words are not used freely, creatively, to make something new, to make a future, they stay rooted in the past where they came from, and root the speaker there too.