The requirement that a preclusive finding must have been necessary to a judgment is rooted in principles of fairness. 'Parties should be estopped only on issues they actually deem important, and not on incidental matters.' Lynne Carol Fashions, Inc. v. Cranston Print Works Co., 453 F.2d 1177, 1183 (3d Cir. 1972). Because litigants are likely to view an issue that is necessary to the resolution of a case as important and to litigate it vigorously, it is fair to give such a determination preclusive effect. See Wickham Contracting Co., Inc. v. Bd. of Educ. of City of New York, 715 F.2d 21, 28 (2d Cir. 1983) (noting that the necessity rule ensures that 'parties to litigation have sufficient notice and incentive to litigate matters in earlier proceedings which may bind them in subsequent matters'). The necessity requirement also ensures that preclusive effect is not given to determinations that did not 'receive close judicial attention,' Commercial Assocs. v. Tilcon Gammino, Inc., 998 F.2d 1092, 1097 (1st Cir. 1993), or that were unappealable by virtue of being incidental to a decision, see Restatement (Second) of Judgments § 27 cmt. h. See also Pettaway v. Plummer, ...