The backstory is that I can't use a mouse wheel or trackpad. Most of the time, I need to grab the scrollbar with the mouse.
Not only is this rather tedious, but because of what I call the War on Scrollbars™, sometimes this isn't possible—they either disappear or they are so thin they are too difficult to grab.
Sometimes I use the keyboard, sometimes I use speech recognition. But the easiest and best way for me is to simply click and drag the entire scrollable area, just like on iOS.