Every single person is different, so everyone’s bike set up should also be different. You can have two people, same height, same age and fitness who could ride the same bike completely differently due to their relative proportions.
One might have a short torso and arms but gangly legs, requiring a higher saddle and shorter frame, the other could be all arms and upper body with short legs, so sizing a bike just on height alone (which many bicycle dealers and brands do), is fundamentally flawed.