Props are a visual cue. You, as the speaker, have a cue that allows you to present and talk about your prop while showing it to the audience; the audience wakes up and wonders what the relevance of this object is. Audiences are hooked on visual illustrations, although the objects and their relevance are described in words.
Even in the most serious of informative speeches, for example those about science, it can work well to put one humorous prop among the other props. This lightens up the serious subject matter. The entertainment value makes the audience more receptive to the rest of the speech.
Personally I love using props. I feel comfortable displaying the prop, it’s my cue to what I need to talk about and I have something useful to do with my hands (they cease to be uncontrollable appendages, as an evaluator once put it).
The only thing with props is don’t use too many.
Science Makes Sense Creationism 