For health systems, there are two types of patient workflows. First, there is practice offered waitlists. Second, there is patient requested waitlists.
Schedulers ask patients if they want to be put on a waitlist. Normally, this occurs when a patient openly expresses anger with their wait time. Many patients are excluded from this type of waitlist, specifically the polite ones!
Many access centers require patients to expressly ask to be added to the waitlist. Many patients do not know this policy and thus don't ask. In addition, shy patients are less likely to be added.
Most healthcare systems do neither of these waitlist workflows. Instead, schedulers frequently tell patients to call back in the morning and see if a slot has opened. Patients wait longer and now have to do additional work to accommodate that!