The reason for the overtaking rules being as they are is the interaction with the other rules for avoiding collisions.
For example if an aircraft follows a line feature by keeping to the right of it then it makes sense to require another aircraft overtaking to be further to the right of the line feature. If it was the other way round, the overtaking aircraft could be in a situation of not being able to overtake without moving to the incorrect side of the line feature.
Head to head - not nice to turn right to avoid colision only to find onself turning towards a faster moving aircraft also head-on. Also not nice to be overtaking and see an aircraft ahead but be unable to turn right for collision avoidance because the aircraft one is overtaking is in the way.
While overtaking an aircraft on it's (incorrect) left, one notices a third aircraft converging from the right. It is now impossible to alter course to the right because the aircraft being overtaken is in the way.
Overtake on the right in the air works best.
On the ground, aircraft are expected to keep to the right when taxying unless ground signals or markings indicate otherwise. The when taxying along a wide grass strip, one should taxy on the right. If one complies with this, then the only option available for an overtaking aircraft on the ground is to pass on the left.
Regards,
DFC