I believe on hard keyboards they are there to assist the visually impaired.
From what you are saying, they are on the iPad keyboard? I can't imagine why they would be on there. No use to blind people as it is a flat surface.
Edit: Now that I look at the Apple pictures, definitely looks like they are there. Perhaps to just try and make it more visually real? Like the page turning in iBooks, lined yellow paper in notes etc.