The only application I can think of was on some farm tractors from the mid-1940's through the early 50's before everybody went to 12 volts. In a situation where there were virtually no electrical components other than a battery, starter and generator, and the ignition system was usually a magneto, it made a little sense, I guess. The tractor gets started once, works all day, shuts down overnight, and fires up again the next morning. A 3-brush generator trickle-charges the battery during several hours of running, and there's little if any load other than the occasional shutdown and restart. None of that applies to a street-driven vehicle!
Jerry
