I've been fighting Banjo Acquisition Syndrome for a bit, and have been drooling over the niceties of old-time banjos. One of the things I've noticed is vintage banjos often have a carved heel, while guitars (or dobros, or mandolins, or fiddles, etc.) rarely do. Why is this?

I realize guitars generally have a slightly smaller heel area, but is this any reason not to carve? Or is it perhaps that people play more "up the neck" on a guitar and feel that the fancy part will impede their hand movement?