With the latest release of the blender_magicavoxel addon, all imported meshes now have a default UV map, whether it's used or not.

This was added to fix lighting issues for the Godot game engine in the following scenario:

• Import MagicaVoxel vox file into Blender
• Export the model in Blender to obj
• Import obj into Godot

More details can be found in this discussion.