There's a useful, if reductionist, craft book on screenwriting called "Save the Cat." The title piece of advice is that somewhere in a story - and early on - the protagonist must do something to endear himself to the reader - show some kindness, be generous, be good - in short, "save a cat."
Is this really vital? Isn't it enough that the proagonist is put upon, that he suffers, that interesting things happen to him?
I've done a quick, casual surveyof books I've read and am reading. Lancelot, by Walker Percy, the title character, in a nuthouse after torching a house with his adulterous wife, is trying to communicate by coded knocks to the rape victim in the next room. Compassion. In Francine Prose's, My New American Life, Lula befriends an otherwise friendless teenager and agrees to hide a gun for some fellow Albanians. Okay, her motivations are mixed, but there's still an underlying likability. In Portis' True Grit, Mattie is on a quest to avenge her father. A sort of twisted version of saving the cat, but I still think it holds up.
Maybe this is part of the reason the classic tragedy is about nobility instead of commoners. It isn't just that falling from a great height is more interesting than tripping over a shoelace, but perhaps because being noble assures the audience that the characters have at least some redeeming qualities; it's a built-in save-the-cat card. Macbeth may be a cold-blooded killer later in the play, but at least we know he's brave at the outset. King Lear is a fool, but we know he's generous and kind. Creon is a blowhard, but he - well, actually it's hard to think of anything nice to write about Creon.
If readers do need a save the cat moment, what does this say about us? I think what it says is really very hopeful. It isn't enough to spectate a series of unfortunate incidents - we cannot engage with a character until we know he is worthy of our attention.
He has to save the cat.