I have never thought it that way; Earthworms are truly essential for the nature to work. I really need to put more thought into these things considering nature .
I believe that everything has a purpose, although not necessarily our own purpose. I have added about a thousand worms to my compost. It was supposed to be a thousand anyhow, although I doubt that anyone counted them. I know that I wasn't about to. My compost pile is about waste high, and fairly wide. What I did was dig a hole in the center, then used a new shipping box and, without taping the bottom flaps shut, I extended the open-bottom box into the hole, added some table scraps to it, then I added a combination of shredded paper and peat moss, mixed with some coffee grounds, to the box, preparing it about three days before the worms arrived. During that time it rained, so the compost pile was dampened. First I had ordered just five hundred worms then, seeing that they all arrived healthy, I ordered five hundred more. When the first load of worms arrived, I added them to the box, and put some more peat moss and shredded paper on top. I picked up the second load a couple of days later, and added them as well. If they are going to do well in my compost pile, they will spread out and downward from the center. If the don't thrive, I probably won't know about it for a couple years when I can use the compost. I expect they'll do okay though, since I always find worms in my compost even without having added any.
Last week my husband met a man in our village. He is looking for worms in large quantities that he would sell to garden landscapers. He said that worms, when ground and mixed with compost, is a very potent fertilizer. He added that worms can also be eaten by people, yuck, hahahaaa. My husband is now thinking of making a little business out of that. However, our place is small and there is not much space for a worm planet. Perhaps if we could buy another lot for that purpose.
That doesn't make sense to me, since earthworms are far more valuable for compost when they are left alive. Their castings make excellent compost and, like everything else, they don't live forever, so you'll have some dead worms there too. Plus, they help to break down the compost.
My husband actually uses earthworms for fertilizer. I would see him catching a bunch and cutting them with the trowel before mixing with soil. That's his ritual when preparing pots or beds for planting. He said that the protein of the earthworm rejuvenates the plants. With the compost, that's another story. We have a planter box solely for that purpose. I don't think he was taking earthworms from there.
I agree with Ken. I don't see the sense of killing the worms. When I catch fish I fillet them then grind the remains and put them in the garden. That adds protein and feeds the worms.