Amother reason is that a prop can "untwist"
..... when you run it through soft ground perhaps.
If it is fixed pitch, and airworthy, you can stake your life on the blades being where they were last manufactured or overhauled to be. Because you
are staking you life on it.
In today's technological world, forget the inaccuracy of charts, and just use a portable optical tach to check the installed one. The optical tach can be calibration checked when pointed at a flourescent light.