The main reason sites avoid this approach is institutional rather than technical. Adding algorithmic mediation invites accusations of algorithmic bias whenever results are unpopular.[0] Simple manual interventions are often sufficient to nudge community behaviour so that majority outcomes broadly align with the moderators’ priors, without the visibility or accountability costs of a more complex system.
[0] Case in point being X. People routinely accuse the new management of "juicing" the algorithm to favour their politics, when outcomes are adequately explained by the exodus of contributors on the other side. Isolating innate community bias from algorithms is a philosophically impossible problem.