There is a big difference between turning away an interested purchaser and how something is marketed. Most timeshares are marketed as something to enjoy with family, and those that are forever contracts market them as a multigenerational "gift" of lifetime vacations to your heirs. While
DVC has specific contract end dates, it was marketed originally as spending quality time and making memories with all the generations of your family. See this 1992 DVC video and how many times they mention "family."