Since when has it been the primary function of discussions to change anybody's mind or to persuade others?

In my mind discussions and ruminations enlarge and clarify one's own view of what one thinks, it exercises the brain, it fulfils a need to be heard, it's of interest to oneself and others, and it's a new viewpoint or a learning process for everyone as they come to it in their own explorations.  It makes for relationship and discourse, and quite often one is looking for something that excites.