Most people are blissfully unaware of all this wild nightlife, and if they were, they would probably try to forget. The point is most neighbors have little awareness of and no inclination to do anything about these night-time omnivores.
Chicken keepers, on the other hand, are passionately motivated to monitor and manage these animals, which once they learn about a food source keep coming back. C.L.U.C.K. is committed to providing prospective chicken-keepers with information about predator-resistant coops, but people who take shortcuts will quickly learn about any shortcomings of their coop design and they will be the people live-trapping predators and calling animal control to come pick them up at $20 a pop.
Snakes are similar, but generally more of a daytime issue. Like the rats, raccoons and opossums, they are already out there. No native snake is going to bother anything larger than a pullet. The notion that the snake population will measurably increase as a result of neighborhood chickens is another misplaced concern.