Consume Product

Part of it might be that pigs are the only livestock that doesn't produce until it's slaughtered. Chickens lay eggs, sheep grow wool, cows and goats can be milked. But pigs don't do anything until you butcher them. I can see why that would make them more economically risky. There's less hedging for their utility.

Also, ancient food preservation wasn't up to snuff for pork. That's why shellfish were bad as well.