Since OS X Lion, the scrollbar on websites are hidden by default and only visible once you start scrolling. However, you can overwrite the default and force the scrollbar in WebKit browsers back like this:
The problem is that Apple introduced this as a Human Interface Design feature deep within iOS. The concept is that gestures should be intuitive and indicators present only whilst interacting. There is an exception where the user is paging (left/right swipe) the a page indicator can be displayed the standard dots you see at a bottom of your iOS home screen. App are going as far as to reject certain apps that do not meet HID design, so adding in scrollbars could get your app rejected potentially if it were to enter the App Store.