So they believe what you say. It would be a waste of time to communicate with your audience if they dont even believe you.
I believe the purpose of design is to make the documents more professional.
The overlap lies in the fact that both essays present an opinion on an idea with the goal showing deep understanding and personal thoughts regarding an entity, with the difference lying in argumentative essays also showing the second side to something, whereas persuasive essays only show one.
If I'm correct the main idea is: They want to know what you want to do the most they wanna figure out what your intrested in the most.