Actually, it wasn't that he "didn't bring slides" for the keynote. There was a miscommunication. (I overheard as the discussions were going on).

Since the speaker was asked to provide his slides a month early in email, he had assumed that this meant that like many 'business' conferences, that the slides would be preloaded on a computer for him.

So he didn't bring a laptop with him, nor even a copy of his slide on a thumbdrive, since he thought that he didn't need to.