I agree that presenters should put most of their effort into their verbal presentation. But also having the essence of what's being said displayed as text is a

I agree that presenters should put most of their effort into their verbal presentation. But also having the essence of what's being said displayed as text is a good enhancement. Comprehension and retention is improved when information is conveyed in multiple forms (e.g. audibly and visually). The combination can be particularly useful when the presentation is not in the audience member's first language. Also in the video you linked to, the presenter was speaking and displaying English which is not his first language and while he's quite fluent, his accent might be a barrier to some in the audience, one that may be overcome by displaying the essential points. The text can also help the hard-of-hearing.