I think it depends on your presentation. If it's like a school project for testing your presentation skills or a mock up presentation, then you have to memorise the whole script. Cause it's not a first hand knowledge, just some fake presentation.
If talking about office projects, sales, etc... then you have concrete content to focus on. What you want the audience to know ? You need to be clear on that. Actually, if you are in this situation, you know what you need to say and you won't miss the point. It's the details that you might miss. Write them in outline.
The issue I see is that linking the outline to form a good presentation is what some people might miss. Don't know how to tell a story from the outline. This requires presentation skills and soft skills in communicating with people in general. How to link up ideas. Practise lah... nothing much can be done from my point of view. Try to take a mock subject and write a few points. Go through the point an turn on your phone camera, record your oration of the points and then review. Then repeat and repeat. Each time, you will think of how you can improve... Doing that, your brain neurons will link up and you develop the skills. Over time, you will be able to do a presentation with an outline of the key points.
The other thing is you really need to know your subject well. eg if you sell a product, you really need to know the benefits, competitive info, etc... it's like learning in school.
I have seen some of my bosses who needed to do face to face or presentations. They will ask me some critical point of the meeting and then they walk in and do a impecable job at it.