Pit bulls are called American Staffordshire Terriers, and terriers are quite capable of a lot of strength (even the small ones) and agility. They're bred for working/hunting (all terriers), highly intelligent, need lots of exercise, they are generally family friendly (when they aren't used illegally), and prey-oriented. They get bored easily. I've owned several dogs (and babysat others) but all had to be trained to not fuss with my chickens. I've had three ASTs and the only dog that I had trouble with was an Aussie shepherd. Even my lab bird dog got trained. So I think the answer is, the owners may not give the animal enough exercise on his own, don't care if he uses his brain, and don't realize his nature is a predator/hunter. But no matter what if the behavior doesn't stop, the neighbors are going to have to put him down. This is on them, and I get so angry at ppl who just let their dogs run amok and don't care the consequences.It depends on where you live, how high the risks are.
I keep my small chickens in a coop/a net covered run attached. The free range a couple of hours each day in broad daylight when am home / on times when there are noises of people and cars.
The clever chickens flee upon the run or over the hedge to the neighbours when they see a dog /large predator on legs. When they chill outside they seek a spot under a chair or bushes against birds of prey I presume.
I had free ranging casualties (missing-not seen any attack) but with 6-9 chickens for 9 years I still can count them on one hand.
I had locked up casualties too. Fox. Rat (chicks).
Loosing chickens / pets is part of life. Avoid it when possible. But not everything is manageable.
@PrairiePeckers
I wonder in what circumstances a dog could kill all 38 chickens? But such a killer like that pit bull is definitely worth a whole lot of effort to get him/her eliminated.