It's really pretty simple. Most timeshare buyers are impulse buyers---and
DVC is no different. You are on vacation. You are having the time of your life. You go on the tour, and are promised the ability to bottle "a lifetime worth of vacation magic at today's prices." A lot of people jump at that without asking a lot of important questions. Can I afford it? Do I really want to return to WDW regularly for many decades? Other things change too: if you move farther away (making flights more expensive/less convenient), or get divorced, or have a new child (or are caring for a parent) which crimps your travel style, etc. Some fraction of buyers *always* discovers that they don't really want it within a few years of purchase.