Some Dragons find it uncouth to rule those lesser mortals. Why rule a nation of Humans, Elves, Dwarves when you could just...relax and allow them to prosper and not deal with such a thing?

Most dragons did not ascend to full Dragonhood from humble mortal beginnings and have a chip on their shoulder from being a slave to said mortals. So, at least in his Draconic Youth, he'll be sure to conquer, pillage, and leave a Legacy and Bloodline through the lands before relaxing back into a mountain top fortress lair of his kingdom.

Who could blame him for such a goal?

Art by the lovely as always  Shadowwolfhunter