It's because the wiimote is mostly designed for movement. Although, it might be an idea to write in to developers like SEGA and Capcom that are making point and shoot games, to include a calibration on those games specifically. What basically happens (from what I can discern) is that it senses stuff like acceloration, rotation, distance etc. rather than a laser. Good for movement, okay (but obviously not perfect, considering different TV setups) for point and click.
I've played Resident Evil 4, and it's controls are really good. I think it's mostly on-rails shooters that suffer from non-calibration. I think most people have just kind of learned to accomodate for it.