But as I pointed out, many cattle are ranched on land that cannot grow grain. They can't grow the sorts of crops that humans eat, only the sorts of crops that cattle eat. If cattle weren't being ranched on those lands they wouldn't be producing edible grain instead, or any other food that humans could eat. So the inefficiency is moot when it comes to the amount of nutrition produced, removing the cattle from that land would simply reduce the total amount of food we have available.
Sure, if you remove the cattle then wild animals could come in to replace them, but we should make sure that's not going to result in starvation and poverty if we do that. Many areas of the world have subsistence ranching by the locals.