But, go back one char is also left arrow. Why do you need another key for that?
I would have to move my whole hand over to the arrow keys, or I can use the edge of my right hand (on a full size keyboard, not laptop) to hit ctrl, and hit "b" with my left index finger.
1) Some keyboards don't have it, or have it in an awkward place. Most Android on-screen keyboards don't have it (good time to plug Hacker Keyboard). The gestures on Blackberry (e.g. Android) physical keyboards act like scroll-wheel movements rather than cursor keys.
2) Some shells/systems/terminal emulators/some TERM= settings/etc. just don't handle cursor or home/end keys in the console, and instead splat out garbage like: ^[[C^[[D^[[7~^[[5~
Of course, a bad setup is a bad setup, and if you're moving your hands a lot because your workspace is poorly setup, you'll also have issues.
For best results, you'll want to keep your hand movements natural and comfortable and your tools within easy reach. Take short breaks to move your hands, as well as your entire body.