The end result is a spoken presentation.
Spoken language is very different from the written. Writing tends to use far longer, more convoluted sentences, which often use voices that we would not use in speech. Try reading out the sentence you just read and see how awkward it sounds when it is spoken.
Again, it is a case of speaking to the audience in their language – the language they expect to hear spoken.
So if you need to write your presentation first, take the time to read it out loud, and then say those same ideas as if you were telling someone face to face. If you absolutely have to have a written draft, then re-write using what you said aloud. Make sure, though, that you can make eye contact.