I think Tessie's cries at the end of the story also point to a fairly negative aspect of human nature. We often don't try to understand or empathize with another's plight until something similar happens to ourselves. When Tessie claims that what's happening to her isn't fair, that it isn't right, she is right. But, as another commenter has already pointed out, it seems incredibly likely that every other person who has ever been the "winner" of this terrible lottery has felt the same way and said the same things. And I doubt Tessie stepped in to stick up for them when they did. She, like everyone else, seems totally complicit until they draw the wrong slip of paper, and then -- and only then -- do they want others to empathize. Therefore, her scream is significant because it shows how ultimately selfish and self-serving human beings can be: if it doesn't affect us, then we are often content to let injustice slide.