In all of my campaigns so far, the backstories of the players' characters have, in one way or another, eventually played an integral part of the story. It helps the players feel that they actually have something invested in their adventures--which makes dying SO much more awful.
But I agree with Zurai that it depends on the style of the GM and players. I run a very story-oriented game where sessions involve almost as must diplomacy, political intrigue, and character development as ogre disembowelment, fireball explosions, and treasure stealing (though I make sure never to go a session without at least one good bloodbath).
This style comes rather naturally to my group, so its still a casual leisure activity for us too. Gamers of different temperament would likely find staying "in-character" exhausting and annoying.