The outcome of the calf is known - sex, color, size, breed, etc. Easy to keep track, project, flow of business. The Canadians are the most advanced with this. The Meat Industry is the third largest in the United States. The US produces the finest beef in the world, bar none.
Society wants protein from meat products.
US citizens consume more meat than any other country. Two hundred pounds of meat per year are consumed by each individual. The majority of the meat that is raised in this country is eaten by Americans. Some people who could afford to import our beef, don't like our hormones. These items are used for commercial enterprises.