How about they use some really effective and efficient facial recognition software.
One that comes equipped with binocular vision, auditory confirmation system and often a nice smile.
It's called a "Human".
Taking a photograph is actually *far* more effective than a digital fingerprint, much harder to get wrong and works for 100% of passengers.
Fingerprints can't be done on many people - such as those who don't have hands!
Many other people have poor fingerprints for various reasons.
Also, consider this:
Person enters terminal, has fingerprint taken. They go to coffee shop, and buy a coffee.
The coffee is too hot, and slightly burns their fingers - no big deal.
Person then goes to boarding gate, and their fingerprints don't match!
It is extremely easy to accidentally change your fingerprints temporarily.
As passengers only spend a few hours in the terminal building, any slight changes won't have time to disappear.
Finally - taking fingerprints takes a long time. Usually much more than fifteen seconds:
1: Boarding card?
2: Please put down your hand luggage and stick your finger on this.
Taking a photograph takes under a second:
1: Boarding card?
2: Please look here, thanks!
The comparison system is similarly slow:
1: Boarding card?
2: Please put down your hand luggage and stick your finger on this.
3: Computer says ***
as opposed to:
1: Boarding card?
2: Hello Mr/Mrs XYZ, welcome to blah.