Many inexperienced speakers rush their presentations because of that fear and dread of standing up in front of a live audience. They cannot wait to bring it to a close.
As long as the message has been delivered and reinforced (usually by distracting and overloaded PowerPoint slides) that's the job done. Thinking about how to win over the audience is the last thing on people's mind but it is absolutely crucial.
It's vital to get the audience on board immediately, otherwise they'll have switched off in the first 5 minutes; that should be regarded as a catastrophe, but regrettably it is alarmingly common.
In recent years I have made a point of asking people what they thought about a presentation that we have all sat through and it is truly horrifying how many people very quickly went off into their own dream world, so dull was the presenter.
It is not uncommon for 100 people to sit through an hour's presentation and only 10 to be still listening after a few minutes