Why should Characters be Equal?

It is often claimed that the many Merit and Flaw or Disadvantage vs. Advantage systems for enumerating the bacground of a character are there to balence out the weird and create equality. This raises two points however:

Weirdness

Where do all these weird caharacters come from? Where are these hordes of disposessed kingdoms whos lords are off adventuring. The best fantasy is usually carved from the basic pretty obvious characters and that assumption is the one some games work happily on. For example in Dragon Warriors and Dungeoneer characters are all even, simple and pretty obvious. AD&D is just another game with that kind of assumption. You don't need rules to explain away the odd backgrounds, there just aren't any!

Equality

I quote labyrinth.... when Sarah says

"That isn't fair" Jareth replies

"You say that so often, I wonder what your standard for comparison is". Why do all characters have to be balenced? Where in fiction is the model of the entirely even party? On the contorary, the usual group will be of many different power levels, just as in time most groups develop splits between faster and slower advancing characters. Roleplaying is not a Wargame, and if we are serious in the proposition that the strength of a character is in his personality and roleplaying and not his combat stats then why do we demand that all characters be equal in power instead of playing with and capitalising on their differences in strength?