The only reason for using the fingerprint is that the first time you go through the turn style your print is assigned/associated with the pass that you hold, making it unique to you.
Your pass + your finger print = admission. You run your card and scan your print each time you enter the park.
This is so the passes cannot be stolen or if lost can be replaced and it also prevents you from giving over the last day of your ticket to some lucky person.

Just read KG2V entry, sorry to repeat.