It does no good to spread a net within the sight of any bird (GW)Consider setting a snare for a bird when it is watching, you would expect the bird to stay away from the looming danger of being caught. Foolishly the bird ignores the snare and goes for the bait and it it ensnared.
Nobody robs a bank with everyone watching (MSG)
Its no surprise that people do things that have grave consequences that are well known to them and they still go ahead without any thought of it. They look at the immediate satisfaction of their needs without the end in view.