There's nothing like the classics. Why does the young hero set forth from their hometown? Because it's been destroyed of course! Be it dragon, evil bad dude, marauding nasties or any other variety of town ending problem that can be killed it's all in the classic fantasy books. I doesn't work quite as well when run though a fantasy campaign, because this sort of motivating heartbreak is usually reserved for the main character. Which makes for a rather amusing tale if everyone's from a town that was destroyed. Doubly so if they were all destroyed for different reasons. Imagine being in a campaign where 5 villages were all eradicated for entirely different reasons, all of them nearly world threatening threats. On one hand you'd have a metric crap ton of plot hooks. On the other hand your heroes would have their hands overfull dealing with their own pasts. You might get complaining players as well if their past isn't dealt with in a timely fashion. All in all a mess waiting to happen. I should try running a game like that someday.