@shapr @bittner @feoh
Those presentations are the absolute worst for people to read afterwards. Slides with a single word on them, all of the context in the soundtrack. Great for not distracting the audience during the talk, but awful if you just have the slide deck. I've seen a bunch of those uploaded after a conference and just had absolutely zero idea what the speaker was talking about.
The other use I didn't mention for slides is to remind the speaker what they're supposed to be talking about. If you don't need this, you often also don't need slides unless they have illustrations that are easier to point to than using words.
One of the best presentations I've seen was from a USAF general. He didn't know he was expected to give a talk until about half an hour before. He had no slides and just a little deck of note cards. I saw them after the presentation, each had a single word on it. His entire plan was 'talk about this for a few minutes, then move onto this' and he did exactly that. Unfortunately, unless you had a recording (and it wasn't recorded) there was no way for anyone else to know what he was talking about afterwards.