Why is the back of a cow not kosher?

The question of what foods are Kosher and what foods aren't comes down to when The Bible was first being written. The Hebrew leaders back then made the decisions as to what Jews should or should not eat. There is some scientific reasoning behind some of the rules, like, for example; pork, if not cooked properly can make you sick because of Trichinosis worms that live in the meat. Telling people not to eat pork will make sure no one gets sick because some may not cook it properly. Other examples are simply based on whether or not a Rabbi blesses a food. Some water and soft drink companies have Rabbis come into the plants and bless the vats.

Kosher animals have split hooves and chew their own cud. Pigs do not chew their own cud.

Kosher food has nothing to do with blessing the food. the mashgiach (kosher supervisor and doesnt have to be a rabbi, makes sure that non kosher substances don't go near the kosher food.