Collecting a Crate causes all Worm names to disappear
From Worms Knowledge Base
Collecting a Weapon Crate in Worms or Worms: The Director's Cut on the Amiga will make the names of all Worms and their current HP disappear. They can be quickly reenabled by pressing the DEL key.
This also occurs after deploying a stick of Dynamite, though in that instance it is less of a tactical inconvenience.