Interesting. Perhaps it has something to do with how I answered his questions...
Right now I'm having trouble getting him to give me more jobs.
You have to be level 20. All I received was a contract from the steward then 2 quests from the Jarl (about the forsworn threat) and then I was able to purchase a house.
Anyways to the OP:
I would save the game; defeat the first dragon and not go to the Jarl, fast travel around Dawnstar and Winterhold/College of Winterhold and see if dragons appear as that is where I see them most. If they do then you have your answer because I defeated the first dragon AND I went to the jarl and turned in the quest and I have "randomly" spawning dragons. I haven't done anything in the story beyond that.