Hi @REI-JohnJ !  I haven't a clue!  At least not one rooted in any verifiable fact.  But, I think that @Philreedshikes has really good points.  The mountains tend to run north/south, and I think that's the main determining factor. The bulk of open land follows along them, so it's easier to create a continuous trail through this open land.  

Here on the east coast, even the short local trails get interrupted by property owners, both private and commercial, unwilling to allow access.