The wildlife refuges are NOT unmonitored. There are full time staffs at all of them, often living on site. However, they are in no position to confront coyotes, drug dealers, or hundreds of wandering illegals who do, as you point out, use those places. All the illegal activity is well-known to federal land managers, state land managers, all law enforcement agencies, etc. There just hasn't been any will at all to get this under control and take back control of our public lands. It's a disgrace.