This is the best most coherent explanation of beef growing operations for a layman that I've seen, and it's from an actual rancher.
The vet I work for is a mixed practice, which means large and small animal. Probably 90% of our large animal patients are bovine, and most of our clients have some cow-calf operations.
Although I actively speak out against CAFO practices, one thing I try really hard not to do is dump on the ranchers. They really have little to do with what happens when they sell or move their steers to a feedlot. Really, the ranching side of the beef industry is quite nice for the
animals. The cows get to spend their lives grazing in large pastures protected from
predators, hang with their buddies, raise their babies without interference, and only get bothered by humans
a few times a year.
Go to the link above and look at a typical rancher's profit margin. Americans want cheap, corn-fattened beef, and there's not much a
rancher can do about it without either going out of business or
switching to a niche market.