I have also wondered about the history of the different point counting methods but have never heard anything definitive. Something traumatic must have happened to eastern hunters that makes them count points incorrectly and hang their deer from the neck instead of the back legs as god intended.
In my opinion, the eastern count lacks enough detail to accurately describe a buck. A 10 point could be a 5x5, 4x6, 3x7, 2x8, 1x9 or even a 0x10. Do eastern guys immediately follow up the total count with how many points are on each side or do they just assume as near to an even split as possible? Why not cut to the chase and just say a 5-pt, or if not symmetrical call it a 4x5?
The western count offers simplicity and descriptive detail. If you say you shot a 4 point, I know it had four points on each side. Or you might tell me you shot a 4x3, I immediately know what you're talking about. One might clarify, in the case of mule deer, that they shot a 4-pt with brow tines. Since mule deer often do not have brow tines it makes sense to compare apples to apples by not including them in the point count. Sure it adds into the B&C score but amongst friends we just want to know you are talking about a true 4-pt and not a 3x3 with brow tines.
I have noticed a disturbing trend among some western hunters to use the eastern counting method when referring to whitetails. I blame social media, hunting TV, and transplants from eastern states for spreading this false and pervasive doctrine. I hope we can all take a stand against this unprovoked attack on our western hunting heritage.