Dialogue is not an open conversation it is a formal discussion between groups or individuals with the intention to teach, learn or evaluate what is being suggested. In many schools, students would memorize notable dialogues that perfectly explained or clearly identified a particular subject. The reason for using them in the community is to keep alive the idea of clear logical reasoning and debate, this also prepares the student to use logical steps to draw conclusions from facts.
[note: I wrote and read a lot more later on dialogue and dialectic methods so I know this isn’t exactly a clear description of why we should use them, or even what dialogues truly are, it’s true that dialectic and dialogues feed the minds ability to debate and reason arguments, the noting of fallacies, etc. are all good reasons to have at least a broad understanding of the discipline, but I wrote more on the subject later.]