Bism Illah wa as salaamu alaykum.
I once used an analogy with some students about why I wear niqab. Obviously, it is not the whole reason...but it puts across the basic concept. A sister commented that this could be used for adults too, so I'm sticking it here in case it might benefit.
I said, "If you had a cheese sandwich every day and loved it, you would be happy and content every day with that sandwich and look forward to eating it. When someone comes along and offers you peanut buttter and jelly or chicken, then you start to become discontent with the cheese, wanting more variety. I cover because I don't want to put more choices in front of the eyes of men. I want them to be content and happy with what they already have."
You may change the examples; they may be toys, favorite stories, even friends, but the concept remains the same. Perhaps it will be useful for some who have a hard time coming up with an answer that people can relate to.