According to The Supreme Court Historical Society, the majority of Supreme Court cases, which is approximately two-thirds, come from previously decided cases in federal appellate or district courts. Justices review prior lower-court decisions, vote on whether or not to accept a case and eventually reject about 70 percent of petitions.
This sources explains that the Supreme Court rejects cases for a number of reasons, including siding with the lower court's decision, determining the case does not meet the status of a national concern or deciding that the Supreme Court lacks jurisdiction to preside over the case. If the Supreme Court refuses to accept a case, the lower court's decision stands. Annually, the Supreme Court receives roughly 7,000 petitions.