Decks get forwarded
More than any other format, a slide deck is passed on. Each recipient sees the same properties: who made it, which company they work for, when it was last touched and how many revisions it went through. A deck sent to a client is often forwarded internally three or four times before anyone reads it closely.
What else hides in a deck
Speaker notes, which are frequently far more candid than the slides. Slides hidden from the presentation but still in the file. Objects dragged off the edge of the canvas, which are invisible on screen and fully present in the file. Comments from reviewers.
What cleaning does here
Blanks the document properties and removes comment parts. Speaker notes, hidden slides and off-canvas objects are content, not metadata, so they are left alone. Delete those yourself before you send the deck out.