In smaller, informal settings, pulling out your laptop to run through your slide deck can zap the energy of a meeting. For these meetings without slides, it does not mean that this is a meeting with a presentation. In the absence of slides, it can be hard to stay focussed on the story line. You might get lost in tangents, you might miss the important punch line as the waiter asks if you need sugar or milk.
The way you “present” in a slide-less meeting is different from when you are in front of a big audience. But still, you need to rehearse that story, maybe even more.