Don't think there is anything in particular that ties bull horns to fixed gear/SS bikes. It may be a "fashion" trend, started by the city couriers who wanted very narrow bars to be able to squeeze through narrow traffic gaps. For normal road riding I use drop handlebars and spend most of the time on the hoods, but when tight cornering, descending and occasions when I need more control, I drop to the drops. Using the drops means my centre of gravity is slightly lower and there is no danger of my hands jumping off the bars and losing control.