Much has been debated about the reason for the Abrahamic religions' ban on consumption of pigs, and of the Jewish and Christian veto in particular. I would like to contribute my piece on that but before I do, I would like to acknowledge another plausible reason why that was so.
This author 1 notes that the geography of Palestine is unsuitable for pig farming due to the heat which kills pigs, essentially, and the inevitable competition between pigs and humans for the same foods because unlike cows, pigs cannot digest cellulose. I would now like to offer a religious opinion.
Jesus 2 says that what defiles a man is not what goes in but what comes out. The context here is His disciples' contentious eating without washing their hands.
In Jewish religion, God prohibits Jews from eating or even touching animals, birds and fish which you will note include many predators and scavengers such as pigs, vultures and scaleless fish. These animals are noted to transmit defilement through contact and consumption.
If you have seen my point, you can stop here and go do something else.
Some of the things that God prohibits these people from eating include things that are torn, things that died by themselves, unclean animals, some parts of sacrifices, blood and meat with blood still inside, strangled things, sacrifices offered to idols and other gods, most insects, most birds and foodstuff that has come into contact with these things.
You will note that most animals that fall into this category are scavengers, predators or do not chew the cud (this latter point harks back to the first point here).
I would like to speculate (this is very dangerous) here that most of these prohibited animals, in their daily course of feeding regularly feed on and interact with various forms of unclean foods themselves, such as dead animals and debris from dead animals, torn animals, wastes from human beinga and other animals, rotten foodstuffs, discarded sacrifices and pagan sacrifices among other things. These interactions make them unclean, and they made the human being who came into contact with them unclean as a result.