Why are the fingerprints necessary? In Disney's words, “We offer the convenience of Ticket Tag at the entrance of many of our theme parks and water parks. Ticket Tag helps to facilitate ease of re-entry into our parks and helps prevent fraud.” They refer to it as a convenience and a fraud prevention measure.

Theme parks, most notably Disney and Universal, use "finger geometry" or "biometric linking" primarily to prevent ticket fraud. Because multi-day passes are significantly cheaper per day than single-day tickets, people used to try to "share" a 5-day pass among different individuals. By linking a specific person's finger scan to a ticket on the first use, the park ensures that the same person is using it for the duration of the visit. From a technical standpoint, they aren't actually "storing your fingerprint" in a way a police department would. Instead, the scanner identifies several unique points on your finger and converts them into a numerical code (an encrypted token). When you scan again, the system just checks if the new scan generates the same number. This process is faster than checking IDs for every guest and helps keep lines moving at the turnstiles. If you prefer not to participate, you can usually opt out and show a photo ID at the gate instead.