I personally think that conflict needed to die down so the girls would accept Lottie's rule (at least for now). Jackie was the only one that was not afraid to say anything against it in the end. Tai doesn't speak up anymore because of Van and probably also because she's preoccupied with her sleepwalking. Nat may say it's stupid, but even she participates in Lottie's rituals now, maybe because she knows she's in the minority or is too tired to fight it any longer or because of Travis. But Jackie could have rallied the sceptical ones around her if she lived and caused a division in the group way too early. She was a great character but she was the last of them that truly held on to civilisation (even Coach Ben stopped caring about the rules during Doomcoming). I also think the conflict between her and Shauna would've been too drawn out if it carried into the second season. Seeing Shauna now consumed by guilt and grief rather than hiding a secret or fighting with Jackie is much more interesting imo.