When we think about the significance of any work we have to consider the importance of the message that the author is trying to convey. In this short story, it is clear that what Jackson is doing is challenging our preconceptions and ideas and turning the mirror of what happens in the story on to us by examining the role tradition has in our lives and how it can lead us to engage in practices that are cruel and inhumane.
Old Man Warner is a crucial character to examine in this regard. He, more than any of the other characters, represents the forces of tradition that are against change, even when change is clearly to be preferred. Note what he says about other villages that have abandoned the practice of the lottery:
Old Man Warner snorted. "Pack of crazy fools," he said. "Listening to the young folks, nothing's good enough for them. Next thing you know, they'll be wanting to go back to living in caves, nobody work any more, live that way for a while. Used to be a saying about 'Lottery in June, corn be heavy soon.' First thing you know, we'd all be eating stewed chickweed and acorns. There's always been a lottery," he added petulantly.
Note the arguments for maintaining the stasis. According to Old Man Warner, any form of change is wrong and is equivalent to taking humanity back to "living in caves." Also note that the tradition of human sacrifice is linked to good crops. Thus Jackson severely challenges us by making us think of what inhumane practices we carry on doing, year in and year out, under the banner of "tradition." Perhaps, she suggests, we are not so far away from these bloodthirsty villagers than we think.