We also have a fingerprint scanner and I still always carry a key. If the fingers are wet or dirty, the fingerprint does not work and since my fingers are not always in "top condition" after walking the dog, it's too risky for me. Also after gardening, washing the car, and other tasks, you can't get in with the fingerprint, or it's faster with the key because you first have to get a dry, clean finger.
Best regards
Sabine