The problem is that they are wild and inaccessible. The original "parents" were domesticated, and had some training in being herded out seasonally. If it made economic sense, they would have been rounded up by the foreclosing bank back in the 70's, but the bank was the second deadbeat with regard for being responsible for their property.

They won't be wasted, though - Ma Nature will take care of that. Feeding the wilderness with their carcasses will be a small compensation for the damage those cows have done to the environment over the decades.

You never change things by fighting the existing reality.
To change something, build a new model that makes the old model obsolete.
R. Buckminster Fuller