When you live in wilderness areas - it's easy to do set-ups like this perfectly safe. There is no colateral damage. trappers have been trapping wolves, coyotes etc, for a couple hundred years wihtout problems. Why would they start now? When your livelihood is being killed by wolves, drastic measures sometimes have to be taken.
As to leaving traps out in the bush - who on God's earth would do that? Like you're going to leave hundred's of $$ of traps out in the bush - not likely.

I assume you live in a city and don't get out much. 'Things' are different in the bush.