Why? Because it's cheaper to do it that way. If you want good meat, find a local butcher. Hey, find a local farmer and pay for a cow.
A couple of years ago, I was at a wine tasting, and one of the women was talking about how she'd have to get up early to go to the Dieppe farmers market, 'cause she wanted this organic butter, and it sells out. I told her, simple solution. Talk to the farmer, offer to buy a cow, he keeps the cow and makes the milk and butter, and you get a guaranteed pound of butter a week. She looked at me like I was crazy, but I explained that a lot of farmers will do this - I know people who buy a beef cow, the farmer raises it, they share the meat. Her husband figured it could easily work, and be a good deal for both parties, and I'm pretty sure he was going to talk to the farmer.