[Data collection fortnight ends today. And then we shall return to our regularly scheduled programming. Until then, here's Rule #1, from the archives.]
If you are giving a talk, or teaching a class, or are otherwise responsible for transmitting content from your brain to other peoples' brains, you should be able to give that talk - even if somewhat modified - without any visual aids. You should be perfectly capable of giving that talk, in the dark, if the power goes out. Because your science is so awesome that your words alone will make people revere you like the science god or goddess that you are.
One of the best talks I ever attended was given by paleontologist Gary Vermeij. Gary, being blind, doesn't need visuals to string together a compelling narrative.
Depends on the subject. Talks on geology are typically heavy on maps and diagrams that matter a lot. I've given up to hourlong power point presentations that had NO text slides aside from the title. Sometimes you just can't live without the pictures.
Also depends on the audience. A lecture class or a general audience, yes. (I was a student back in the chalkboard era, and there were good, dynamic lecturers back then.) An audience consisting of specialists in your field will want to see the data.