What will you do when you cease have fingers? What then?!
Biting your nails is a bad compulsive habit for many reasons, an obvious one includes introducing bacteria, organisms from your hands, to your mouth. Even if you wash your hands often, do you really wash beneath your fingernails every time? Think about it, the same hand you wipe your "bum" with, despite being washed with water and soap is still going to carry some germs from your anus and then it's going straight into your mouth. There have been past reports of severe deformities of the nails due to nail biting. I mean yeah it's delicious, but you gotta care for those hands!