In the previous chapter, we talked about how users hate reading, and will avoid it unless they absolutely cannot accomplish their task. I don't mean this literally. What I mean is, you should design your program so that it does not require a tremendous amount of mouse-agility to use it right. Some people are new to computers and have not yet developed the motor skills to use mice accurately. Some people literally will never have the motor skills to use mice precisely, and never will.
Many people find that it is extremely difficult to double-click without slightly moving the mouse.
As a result they often drag things around on their screen when they mean to be launching applications. You can tell these people because their desktops are a mess because half the time they try to launch something, they wind up moving it instead. Even in the best of situations, using the mouse a lot feels slow to people. If you force people to perform a multi-step operation using the mouse, they may feel like they are being stalled which in turn makes the UI feel unresponsive, which, as you should know by know, makes them unhappy. In ye olden days when I worked on Excel, laptops didn't come with pointing devices built in, so Microsoft made a clip-on trackball that clipped to the side of the keyboard.