well, they used to be, the old magnetic ones were exactly that, basically a choke coil or a small transformer, but newer more common electronic ballasts are really just high frequiency high voltage SMPS(switch mode power supply). and are more like the PS in a computer than the transformer in an arc welder...
and when you really get down to it, isnt the ballast really just a current limiting device? i mean, voltage step up and frequiency increasing are both great for noise, and efficency, and the life of the bulbs, but you can fire a flour bulb without a ballast, but the bulb wont last long and will self distruct if the current isnt limited...