What is the point of reading fingerprints when visiting an amusement park, or for that matter, any ID whatsoever? It's been several years since I went, but the only time ID was an issue was for a Disney cruise, where passports were required due to a stop in the Bahamas.
As long as you've got cash or valid plastic, I see no valid reason for an amusement park to demand any kind of ID.
It's because of their parkhopper pass - they REALLY don't care WHO you are, just that "person with fingerprint that reads on OUR scanner as #123456 who bought pass #12" is still the same person trying to use pass #12 later that afternoon at another park