Input devices for scrolling are not universally available. Wacom/pen users don't have a scroll wheel. Many trackballs don't have a scroll wheel. Some have a s

Input devices for scrolling are not universally available. Wacom/pen users don't have a scroll wheel. Many trackballs don't have a scroll wheel. Some have a scroll ring around the ball though. I got RSI in my scrolling finger, so I removed the scroll wheel from my mice. And there have been times that I have overstretched my mouse-arm and had to use a trackball with my other hand for a few weeks.