Most professors and public speakers have a few good stories and quips they especially like to use. In my experience, most of them seem to come from one of three people: Mark Twain, Winston Churchill, or Yogi Berra.
I once tried to search the online collection of the complete works of Twain for two of the sayings. No luck. Zero items found. But I still like them, so I try to remember to say, "As Twain said, according to some attributions, ..." A professor friend of mine once asked his two research assistants to find the origin of an important insight attributed to General George Marshall: "There is no limit to what you can accomplish in this town [Washington], if you're willing to give someone else the credit." Again, no luck. No proof that Marshall ever said it. I still cite the statement, for the very absence of definitive proof somehow makes the truth of it even clearer.
I still believe in trying to verify statements attributed to others, and I welcome those researchers who can prove that Washington/Franklin/Lincoln or whoever did not in fact say some widely quoted line. But if I can skip the footnote, some of these sayings and stories are too good to check.