"Don't quote me." -- Mark Twain (not)
Someone mentioned the other day that they had listened to a program on NPR about all of the quotes attributed to Mark Twain that he never really said. I was disappointed a bit that Twain never said, "“Everybody talks about the weather, but nobody does anything about it,” but I wasn't surprised. As a Journalism major, I learned very quickly that very few people speak eloquently enough to actually get a coherent quote for them. Thus you paraphrase.
As a PR writer I also learned that the best quotes for your press releases were the ones you wrote yourself and got your CEO to approve. The same goes for speeches. We all know (or should know) that President's of the United States don't write their own speeches. That is why they sound so articulate (George W. Bush being the exception...you have to be able to read in order to deliver a good speech).
I imagine most quotable quotes are probably contrived in one way or another. Let's face it, unless you are making a canned presentation, very few people spout original prose worth remembering. Case in point is a conversation I heard at the train station this morning:
Station agent (to female customer): "Morning, how are you?"
Female customer: "Oh, it's Friday..." Hilarious laughter.
End of conversation.
Even if you do spout something worth quoting, chances are you stole it from someone else.
You can quote me on that.