IPhone : Swift scrollview's subview count in storyboard

class ViewController: UIViewController {
    @IBOutlet var storyScrollView: UIScrollView!

    override func viewDidLoad() {
        super.viewDidLoad()
        var scrollTemp = UIScrollView(frame: CGRectMake(0, 0, 400, 600))
        view.addSubview(scrollTemp)
        println(scrollTemp.subviews.count) //0

        println(storyScrollView.subviews.count) //2
    }
}

my storyScrollview in storyboard is empty. really empty..but storyScrollView.subviews.count is 2.

if you can't believe me. you can test same code.

but when I create a scrollview manually. scrollTemp.subviews.count is 0.

They are same scrollview. difference is just storyboard using and hardcoding.

and two subviews of storyboard scrollview is UIImageView.

Do you know why?

when I created scrollview through storyboard why default have two subviews?