What WizofOz said.
RPT serves the major population hubs already, so no need for a more expensive option no matter how convienent it is.
In the US the population is all over the place (look at what is defined as LA and then tell me where the low population part is between there and San Fran for example. There's people everywhere and they all need to travel through the hub and spoke system the RPT's have. Pain in the arse if as Wiz said you want to go from regional to regional.