Why do you want to waste the first incredibly valuable seconds of a speech engaging in an activity for which you have not had previous training, sending your listeners off on a mental tangent--inviting comparisons with professional comedians who really can tell a joke, or worse jeopardizing your credibility? You should be "hooking" the audience with your content, not using them as comedy club guinea pigs. It is not that I lack an appreciation of humor. But I know that humor is hard and its use has to be earned. Or as we say in acting world, "Dying is easy, comedy is hard" (deathbed quote variously attributed to actors Edmund Kean and Edmund Gwynne.)
And it's not just jokes. This weekend someone told me the best advice he got in a college course on public speaking was to open with a humorous icebreaker. When I shared this with a colleague, he suggested that there must be a book of such quips floating around, because he has heard a few of them on multiple occasions--from different people. I have had this experience: shifting uncomfortably in the audience upon hearing the same mildly humorous line spoken for the fourth time in as many speeches by a respected, notable speaker. Why does she diminish her brand with this attempt at "funny"? A comedian can have a comic "catch phrase," but is it really appropriate for anyone with a more serious job?
The reason always given (and I just heard it again this weekend) is that starting with a humorous line "relaxes the speaker and relaxes the audience." But watching an audience suppress the eyeroll and groan that accompany the thought "here we go again--another content expert who wants to unleash his inner comedian on us" does not a relaxed speaker make. So you reflexively turn a blind eye to the audience reaction in the opening moments, when you should be making a strong initial connection! And trust me, there are ways to achieve relaxation at the podium that are more effective than trying to regain momentum after you "bomb" with your first quip. Because unless you know your audience extremely well, know their cultural background, know their sense of humor, and have practiced your jokes and your humorous stories for timing and rhythm, you will bomb with someone there. Why take the risk?
It all boils down to ego. Because in a business setting, unlike a comedy club, no one will boo you if your joke falls flat. And if your core message is in demand, you will be asked to speak in spite of your propensity to be NOT funny. But do you really want to be that guy -- the one about whom people say, "It's funny: for such a smart guy, you would think he would know he can't tell a joke"?