The reason why scrollbars are not a first class UI widget in mobile UIs is because they are finger based, which means every manipulable widget needs to be finger sized. Making scroll bars finger sized takes up way too much screen space in mobile UI, so they were regulated to a passive progress bar indicator and the scrollbar actions were moved into swipe gestures instead. With that change you lose the ability to prec…
Touch scroll bars don't need to be precise because most of the time we can just scroll normally. But it's nice to have an ability to jump to a specific part of the document in a consistent way.