To make a change happen.
No change, no point. A presentation that doesn't seek to make change is a waste of time and energy.
Before you start working on your presentation, the two-part question to answer is, "who will be changed by this work, and what is the change I seek? "
The answer can be dramatic, "I want this six million dollar project approved."
More likely, it can be subtle, "I want Bob to respect me more than he does."
Most often, it's, "I want to start a process that leads to action."
If all you're hoping for is to survive the ordeal, or to amuse and delight the crowd, then you're not making a presentation, you're simply an entertainer, or worse, wasting people's time.
Change, of course, opens doors, it creates possibilities and it's fraught with danger and apparent risk. Much easier to deny this than it is to embrace it.
Every element of your presentation (the room, the attendees, the length, the tone) exists for just one reason: to make it more likely that you will achieve the change you seek. If it doesn't do that, replace it with something that does.
And of course, you can't change everyone the same way at the same time. One more reason to carefully curate your audience with your intent in mind.
If you fail to make change, you've failed. If you do make change, you've opened the possibility you'll be responsible for a bad decision or part of a project that doesn't work. No wonder it's frightening and far easier to just do a lousy presentation.
But you won't. Because the change matters.