Why people in the desert not familiar with pork and beef?

Well, they're familiar with it, but cattle need a lot of grass and water to raise, and that's not so easy to come by in the desert. As for pork, it not known for sure why they decided it was trayf (unclean), but pigs like to wallow in the mud to stay cool, and will eat anything. They're pretty clean in the wild, but the way humans keep them will turn your stomach. There are conjectures that ancient Hebrews noticed a corellation between certain diseases and pork, but who knows?