Verified answer

Maybe because if something that doesn't kill you makes you stronger- if it DOES kill you it makes you stronger still. ^_^

Death (or near-death) seems to bring out some understanding/insight or enable sufficiently strong-willed people to fight to come back, making them stronger still. In anime, this also happens to Son Goku (Dragonball), Yuusuke (Yuu Yuu Hakusho) and probably a whole bunch more I'll remember after I finish writing this.

Not just anime does this and gets away with it-

Lord of the Rings---> Gandalf (The Two Towers)

Chronicles of Narnia---> Aslan (The Lion, the Witch and the Wardrobe)

Harry Potter Novels ---> Harry Potter (Harry Potter and the Deathly Hallows)

Most any Vampire/Undead series (I'm not going to detail them, there's plenty)

Death and resurrection are a strong theme in lots of writing, so despite possibly cheapening and 'defeating' the finality of death, when used correctly, it can be a great turnabout in an epic story. I just wish that it wouldn't be so darn overused, you'd think some kid is popping quarters for 'Continues' in some stories. @.@

Because he has the will to save his friends and over come the situation...often unlocking him new powers and also because everything is planned out the way Aizen wanted it to. everything happened because he made it so =)

because ichigo is a baddass motherfuker , he doesnt give up that easily