In the corporate world, outlines are still pretty much mandatory at the start of a presentation. Also, they are pretty much wasted time.
Outlines have a very simple purpose: to provide peace of mind. That’s what any audience is looking for at the start of a presentation. They want to be sure that it’s safe to follow you on your journey. Or at least that it’s worthwhile. That their time is invested well listening to you.
“What is it exactly that she is going to tell us?”, i.e. an outline, is one way of providing that peace of mind. But not the only one. Another way would be to have a strong opening that makes it totally obvious: “Where is she going with this?”.
But there are others.
What’s actually more important than how you provide that peace of mind is to make sure that i) your audience trusts you that you know where you’re going with this and ii) you’ve made it obvious to them that it’s ok to trust you, i.e. that you’re leading them to some place they actually want to arrive at.
Whether that actual place is obvious from the start is secondary. Whether you mark it using an outline or other means is secondary.
What’s primary is that you need the trust that it’s worthwhile to follow you there.