The real reason your sapient dragon character needs a "rider":
Dragons on the wing are vulnerable to being mobbed by smaller, more agile flyers, particularly in your large rear blind spot, like a bird of prey being mobbed by crows. Having a human armed with a long spear perched on your back helps to dissuade anyone from getting any funny ideas.
Breath weapons are impressive enough on the ground, but in flight they're really only good for strafing stationary targets; trying to use your breath weapon in an aerial dogfight is a good way to get fire up your nose. A real fight calls for sterner measures – and, concomitantly, a crew to aim and reload the cannons.
In today's competitive world, it's not enough to devour a flock of sheep and call it a day if you want to keep your edge. You're accompanied at all times by a qualified personal alchemist tasked with carefully regulating your internal furnace to ensure peak performance, and sometimes you even listen to them.
No dragon of any quality would be caught dead without their valet. It's not as though you can announce your numerous long-winded titles yourself when introductions are called for, can you? You suppose next you'll be expected to pick up the spoils of your conquests yourself, like a common brigand. Perish the thought!
