Livestock oats do normally have the hull still on them, and oat hulls are difficult to remove (and totally inedible for us, not to mention nasty in your mouth!). There are machines that will hull oats -- that's how they hull the oats they use for making oatmeal, or oat flour, for human consumption. The machinery is expensive, though. Back when people used to grow their own oats to eat, they grew naked oats, or hulless oats. But these have a lower yield than the hulled varieties, so aren't grown commercially in large amounts.