People crave closure. We like books and movies that wrap things up and say "The End." At the conclusion of your presentation, your audience wants you to wrap up the loose ends and bring everything into perspective.
Most mediocre presenters close their presentations by saying something like this, “Well, that’s it. Are there any questions?” There may be a question or two, then, realizing she is out time (or past her time), the presenter say’s, “It looks like we are out of time. Thanks for coming." There is nothing wrong with that type of closing. It is an acceptable and mediocre way to close.
The outstanding presenter chooses a different closing. Rather than closing on the thoughts of an audience member, the outstanding presenter allows time for the audience's thoughts and comments throughout and several minutes before the conclusion of her presentation. She saves the last few minutes for her strong closing, i.e, the message she wants her audience to remember long after her presentation. Then she ends with a simple and powerful, “thank you.”