Why do you think the village needs a scapegoat in "The Lottery" by Shirley Jackson?
I think the village still needs a scapegoat because they are keeping up old and archaic traditions for the sake of tradition. The story hints at an original reason for the lottery. Mr. Adams is talking to Old Man Warner about other villages starting to give up the tradition of the lottery. Old Man Warner scoffs at the idea, saying he thinks those other villages are full of crazy fools. Old Man Warner then mentions a little phrase about the possible origins of the lottery: "Used to be a saying about 'Lottery in June, corn be heavy soon.'"
It seems the original lottery needed a sacrificial scapegoat in order to secure better crops. A person would be sacrificed and killed by a public stoning. The people probably believed this led to a good rainy season, which would lead to a good crop harvest in the fall.
Based on my understanding of the story, Old Man Warner is the only person who still remembers that phrase. That tells me the stated purpose of the lottery is not for securing better crops. The people need a scapegoat because that's all they remember needing.