because any switch in the psp has either a ground or a positive connected to it so it would never allow a clean connection to turn the camera off and on, hence a ultra minature switch can be used, i have some of those exact ones myself they are small enough to fit in most places in the psp, behind the wifi board is a good place to put switches as there is always room for lots of stuff there, just cut a small rectangle in the case so you can switch it on and off.