It's intentional. They don't pay enough to give them the ability to change their life for the better, get away, and flip on them. They pay enough to fill greed, but little enough to keep them trapped and unable to flip, just hoping for more bribe money.

The people they get to do thusxarent smart, they are dumb and greedy. Once involved in a crime that carries execution penalties, they are trapped with no out. They sold their lives for nothing.