Moral behind cracking

Can you guys tell me, the moral behind cracking?
Cracking (as far as I know) is stealing username and password from databases, that means, stealing people's accounts.
Why do you crack accounts? I'm not saying is not moral, I would like to know your opinion about the morality of this

its an interesting debate. if you leave the account with the same password and still let the owner use it, i dont really see the issue haha :P