A Vampire's Bite action is described as:

Bite. (Bat or Vampire Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one willing creature, or a creature that is grappled by the vampire, incapacitated, or restrained.

Does this mean a vampire has to succeed an attack roll and the target has to be willing/incapacitated? Or are these requirements mutually exclusive? It seems odd to me that you can miss when biting a willing target.