A good question. What is it about quotations that captivate those of us who like them? I have books of quotations -- by the Founding Fathers, by Abraham Lincoln, by various theological authors, etc. Why? What is it about the words of others that is so appealing? Partly it is authority -- the use of words by notable authors to support my own contentions. It allows me to speak without using my own voice. But that, I think, isn't the main reason. The main reason is joy in the phrasing and wisdom of others. What I like about quotations is the ability to reference a particularly well-put point or insight, and to share that literary or verbal excellence with others. That to me is why quotations are so interesting.
As Lincoln once quipped, "For those who like that kind of thing, it's the kind of thing they like."