Certification denials are not generally appeallable. Even though denial of certification may be the death-knell of a class action, denial of certification is not an accepted exception to the finality rule. Whether a class is certified, therefore, has a dramatic impact on the respective parties' willingness to settle. Nothing to lose but a contingent claim. Concern that plaintiffs' counsel will cut deals and sell out the rest of the class.
Some states make an evil defendant pay winner's fees.
Attorney's fees must be approved by the court. Sometimes class members who are not satisfied by their share will litigate the size of the attorney's fees. Absent class members must receive notice of any settlement. If settlement bankrupts the defendant, the plaintiffs may get less money than if the defendant maintains some revenue. Class action members have less direct control of settlement demands than traditional clients.