Answer:

1. To make it more exciting and surprising.
2. For me, giving wrapped gift, because you can see the emotions and expectations of the receiver if what'd be inside that thing. Compared to unwrapped gift, they'll only feel happy and no more excitement
3. Giving a gift with wrapping paper is like the way of expressing your love and gratitude to whom you're giving the gift with. Just like whenever I received a gift with properly wrapped, I was so happy, I feel special and loved.