Isn't it because Japanese developers (as well as the audience for jRPG's in Japan specifically) love the idea of personal growth, most easily shown in a teenage protagonist outgrowing his issues? I have read developer interviews saying that this is the reason for such whiny characters, although they didn't use the word "whiny".
A game I'm developing with some friends:
www.xnagg.com/zombieasteroids/publish.htm
It is largely a technical exercise but feedback is appreciated.







