That's because most mobiles use 2D sensor. On the card is the 3D sensor so small scratches or other damage to the finger will have no effect. Of course if you lose most of your finger it will cause problems. But then you can just scan another finger as a backup.
I'd rong bata raha hy
Without charges abhi tak government ne allowed nahi kya he Kam charges mil jayenge bilkul nahi lage aisa hota nahi he