When reading a document in a browser, I rely on the scrollbar to know things like: how long is it? Where am I in the document? How much of the document is on my screen right now?
This is critical for decisions like: "Should I read the whole thing?" and for building a mental map of the whole document.
I use the scrollbar to scroll between parts of the document if I need to flick back and forth quickly, say between the data and the interpretation, once I have that mental map and know where things roughly are.
Yeah, I could literally accept a non-clickable "scroll gauge" to be there all the time that will not be a click/drag target.
I can generate scroll events or use keys like HOME/PGUP/PGDN/END or even search forward/back via keyboard to jump around. And I also suffer when a slightly misplaced click causes a disorienting scroll instead of hitting some other interaction target near the window edge.
This is critical for decisions like: "Should I read the whole thing?" and for building a mental map of the whole document.
I use the scrollbar to scroll between parts of the document if I need to flick back and forth quickly, say between the data and the interpretation, once I have that mental map and know where things roughly are.
While reading, I'm dragging or wheeling.