Everything is wrong with reading your slides. Really...don't do it. In fact, your slides shouldn't have much text at all, because it's a distraction from where your audience should be placing their attention: You.
Ideally, you should never need to look at your slides while giving a talk. Every time you turn away from your audience, you lose a little of their attention.
That's way overstated. Just don't only read your slides verbatim. Some people may not be able to see slides because of obstruction or their vision, so repeating key points is almost a courtesy.
I appreciate it when a slide is a visual piece with limited text, and the notes are roughly true to the spoken portion (for when slides are distributed after a talk).
It really isn't. Your goal should be to have no text, and never look away from your audience during a talk.
You can (and should) repeat key points, but every time you read, you lose your audience. And yes, you can have a little bit of text -- but since most people go too far in the other direction, it's best to aim to eliminate text entirely.
Slides should be simple graphical content to provide signposts and communicate things that otherwise cannot be expressed vocally.
I think you're overshooting in your advice in the service of preventing the bigger mistake of turning around and reading slide contents verbatim (on which I certain agree with you). That's fine, but for veteran presenters, I think your advice is wrong. First, you should have text because you lose your audience no matter what (sneezing, emails, bathroom, etc). You should let them recontextualize and that involves judicious use of text. Also, everyone asks for slide decks after talks and they should be useful in that case even without a recording. Lastly reading doesn't mean, "turn away from your audience and read", it is the same as repeating key points - this can be done for emphasis or pacing, as long as it's intentional. This is my opinion based on my experience, at least.
"Also, everyone asks for slide decks after talks and they should be useful in that case even without a recording"
I am happy to provide copies of my slides, but no, I am under no obligation to make them useful without me presenting them. They're my tools, not your reference.
IMO, this expectation has been driven by bad presenters leading people to believe they can get the same content without bothering to show up to the talk. Maybe that's true, but if it is, you should wonder why you're giving the talk at all.
If your slide contains a picture, whose details you're describing (say for instance a medical photo or city zoning plan or something), certainly you want your audience's visual attention on it as you're describing its pertinent specifics.
Smart people always vastly overestimate the technical interest level of their audience. Even in audiences composed exclusively of brilliant, technical people, the average level of commitment to whatever you're saying is damned near zero. Accordingly, you must keep your message exceedingly simple. Thinking is hard for everyone, and you have to persuade people to do it. It doesn't come for free.
You may not like "marketing", but you're giving a talk to sell a vision. Always. Once you win people over, they'll seek out the details for themselves.
