Call waiting notification for Outgoing call

I have used both android and iphone both and using same sim I have noticed that android is able to show if other user is in a call and give a notification saying "call waiting". In Apple this notification is not shown. This is a useful to feature because after few rings we can hang up the phone knowing user is in another call. It's also not annoying for that other user also with his/her phone continuously ringing while in another call. Why is this feature in android and not in Iphone?