Well, one other reason the Carter (chest) style works better is simply that you're playing the strings in the middle of their length. Plucking next to the ends gives a much different sound, lacking in some harmonic richness, but with its own punchy sound. Most people like the richer sound, and like having nothing on the thumb side of the plucking hand to interfere with movement. Playing "below" (to the right of) the chord bars restricts your hand, and the thumb tends to hit the chord bars.

Kilby Snow's playing is a good example of the punchy, treble-end sound you get playing to the right of the chord bars, and I have to admit it's fun to use his "lean against the chest while resting on a knee" posture, but I usually go with the Carter "flat against the chest" method.

Oscar Schmidt did make a more guitar-oriented version, I forget the model name, a lot longer and with fewer strings, and the chord bars much further "up" in the middle of the instrument. I got one on eBay once, to experiment with, but it was damaged so I returned it, and can't tell you how well it worked. I have seen a bit of film of Maybelle and Sarah from the mid-50s (?), with Maybelle playing one of them.

Bob