Worms are kind of icky things. They live in the ground, and they are slimy. But a maggot is a worse kind of animal in that it usually lives within dead flesh, and lives off of the dying animal or person. There they are “worse” in some way.
These animals are identified as benefitting from death, and in the scheme of things in the Bible, it would seem they are also the servants (or very similar to Satan) who has pleasure in dying and death. This is a great problem as far as holiness is concerned. Something that touches or handles a corpse (animal or human) becomes unclean, so a maggot would basically be an animal that craves and has great pleasure in wallowing in death and uncleanness.
Hell and maggots
Our concept of hell being filled with maggots would come from their association with death and dying.
Isa 14:11 Thy pomp is brought down to the grave, and the noise of thy viols: the worm is spread under thee, and the worms cover thee.
I believe that has a reference to those people covering themselves with worms, as if there were some kind of cold or they sought protection from some kind of discomfort like a person in the cold, and they would cover themselves with worms. Although it does not talk of cold in hell, but a covering as if somehow that would alleviate some of their grief (which it doesn’t).
A maggot is a type of worm, and it is connected with the eating of dead bodies, so it is unclean, and related to death in the Bible.