It's a thing called humor. Many humans, even older ones with an actual profession seem to relish it. This even includes some great academic minds like Einstein and Feynman, whose accomplishments could dwarf those of most other humans who dislike this humor thing.
It has been observed by prominent humanologists however that in certain grey corporate circles (especially in protestant-derived cultures) it is frowned upon -- much alike in our own professional culture here on Vulcan.
This is a college, the audience is teenagers and the lecturers are academics. They don't experience any need for professionalism and I don't think they should.
It's weird and a little tone deaf but a common older brand of humor. The speakers (in general, I only skimmed a few of the videos) don't seem to share it.
