One could need to calibrate camera in a process apart from the actual scan project when the poor object's texture is expected to deliver very few feature points so it may lead to a weak estimation of lens inner parameters. The same applies to the case an object that fills poorly the frame in most photos of the project, specially near the frame borders.
But it just makes sense if your camera lens setting can be fixed the same for both calibration photo set and photo-scan one. Therefore, precalibration of non-metric cameras is usually unpractical for several reasons: It's sometimes hard to have the calibration pattern with right dimensions to be shot at the same distance as the actual object. If the calibration board/screen is not available during the scan photo session and viceversa, its likely to happen changes in lens parameters in the meanwhile. Most p&s cameras and also many dslr lenses lack of the desirable mechanical stability, and lens parameters may change significantly in spite of any care when you shut down the camera, go to somewhere else and then turn on again.