To be a great storyteller, you have to read your audience at all times when delivering your stories. Are they crying? are they laughing? They look confused. Are they typing email? You're trying to figure out what's working, what isn't working?
Are you having the intended effect on your audience? Or are you confusing them? What works with one audience might not work with another with some audiences, you may need more detail, more repetition. There's something about live performance, whether it's the theater singing or Yes, just giving a speech or presentation. That makes it better. And that is you can react to your audience, you can read your audience.
You're not just up there, like a video projector where someone hit on and you're just going through the motions. That's not what any great speaker does. If you're going to be a master storyteller, you've got to be comfortable enough with your material and your stories, to really be present with your audience to get them to listen to them to figure out what effect Are you having on them