At this point in time, it is absolutely trivial to pre-record whatever you'd like, and it will look glorious, and it doesn't need any basis in reality.
As a customer, when you show me a video, I default-assume you're lying.
Also, as a presenter: If your live demo fails and you can't turn that into a win, maybe you're not good at presenting. Your audience wants you to succeed, it takes a minimal amount of charm to make it work. (Heck, even Mark turned this into a win, and he's not exactly a charm bomb)
As a customer, when you show me a video, I default-assume you're lying.
Also, as a presenter: If your live demo fails and you can't turn that into a win, maybe you're not good at presenting. Your audience wants you to succeed, it takes a minimal amount of charm to make it work. (Heck, even Mark turned this into a win, and he's not exactly a charm bomb)