Lots of people claim the reason cats present dead animals to their humans is because they are trying to teach the human to hunt. (Mental Floss, IFLScience, LiveScience) At one point I probably agreed with this. This conclusion rests on cats treating their human as a kitten.
I wonder if there is something else at work.
We also think cats were domesticated about the time humans took up farming. Mice invaded our storage facilities. Cats were useful for hunting down these rodents, so we fed and bred the nice ones. This selection of nice / tame behavior traits also bred juvenile characteristics the same as we see in dogs and experimentally the Russian foxes.
What if the presentation of dead animals is a mutated behavioral pattern? My idea is the cats present these carcasses to tell the human:
See, I am fulfilling my part of our bargain. I killed the pest for you. Reward me.
We humans have just forgotten why it is we domesticated cats in the first place. Cats just have no reason to change the behavior. Out squeamishness is not enough to quash the behavior.