Why is it that an appropriate quotation is an old device that works well to begin a paragraph?

Actually, I disagree with this statement and advise my students to never begin a paragraph with a quotation. In my opinion, when a paragraph begins with a quotation, the reader has no context in which to put the quotation and not a clue as to why it is there. A quotation should only be offered in support of one's own ideas, not as a substitute for one's ideas, and leading off with a quote, in...

Actually, I disagree with this statement and advise my students to never begin a paragraph with a quotation. In my opinion, when a paragraph begins with a quotation, the reader has no context in which to put the quotation and not a clue as to why it is there. A quotation should only be offered in support of one's own ideas, not as a substitute for one's ideas, and leading off with a quote, in an introduction, conclusion, or body paragraph is telling the reader you are not expressing an idea for yourself. A quotation is best used as the middle of a sandwich. Offer your idea. Then offer a quote to support that idea. Then make a connection for the reader between your idea and the quotation.