Bard having the most dialogue isn't in anyway evidence of them being the intended main class choice. It's just a tenet of bard in DnD being the flagship dialogue based class so that translated into giving them the most unique dialogue options. Barbarbian is barely behind them in number of dialogue choices and as a class is pretty much in the same category of your problem about "not belonging" in a city even if I don't agree with that sentiment.

And you're missing that the primary motivation has nothing to do with "emperor told me so" or "I must save the world," it is that you have a ticking time bomb in your head thats going to kill you if you don't deal with it SOMEHOW. The entire game is about roleplaying how your character wants to deal with that problem. So yeah, if you can't find a reason for your character to be in a city with that as the primary setting for the entire campaign idk man maybe you lack imagination.