Special Attack Life Drain doesn't roll for attack

[Delgored]

On Monsters such as the Will O Wisp and Wight, the Life Drain ability doesn't roll to attack. It just automatically succeeds

The Wight has +3 to hit with this ability which is listed.

The Wisp has +3 from Dex, but it is not listed in the attack description.

Life Drain. 1d4 CON damage. Death if reduced to 0 CON.