Now that im thinking of that. Calibration was useful to manually set the maximum value of an axis. For example you could have a joystick to work as an e-brake.
1. Holding it down
2. Clicking on the "C" button
3. Letting it go to its center
4. Lock all the axis
So i guess if you remove it, then the people who use this trick won't be able to do that anymore, unless you have a way to manually set that.
Instead of having the full range of an axis to do something, "split" it into 2, + and - of the center.