When you fly a plane, you do a pre flight check each time before you leave the ground. You don't complain about redundancy and you don't wait until the day before the wing falls off to make sure it is securely fastened. You never know when that day will come, or if it ever will.
The idea of calibration is to make certain the GPS locator is pointing to the correct longitude, latitude, and altitude. Most of the time recalibration is not necessary, and it may never be necessary. However, as responsible pilots, we are concerned for eliminating every possible error before we leave the ground and before it is too late to correct it. Redundancy is a proven technique for increasing a pilot's safety record.
Not only should we be recalibrating at every new site and on every new day, but we should be checking for cracks, bug damage, buildup on the motors, prop damage, wind speed, other things flying in the air, wildlife in the area, power lines, and in general, any obstacles in the environment including properties we might damage with a collision.
When I hear hacks talking about how unnecessary it is to do a recalibration I roll my eyes thinking they will be posting the next "I didn't see that coming" thread.