Despite the cruel factory versions of these rituals that are often practiced today, both Jewish kosher shechita and Islamic halal dhabīḥah were originally intended to be merciful.
Dr. Temple Grandin has published extensive evidence that inhumane slaughter harms every creature involved in the process – not only do the animals suffer, but the people who perform the slaughter are psychologically impacted as well. And the cost of inhumane slaughter is higher, when done on industrial scales, than processes that minimize cruelty, so the factory owners are losing money. There are negative effects for consumers, too – although there’s not a lot of evidence that the carcasses of animals that died traumatically are actually unhealthy to eat, the meat of livestock treated ethically is of provably higher quality. Many people dislike the taste of meat from animals killed in fear and anguish; it is measurably chemically different due to bruising, hormone release and similar effects.
Today most people are divorced from their food sources, and will happily eat a cheeseburger while decrying the cruelty of hunters. They don’t seem to have any idea how much unnecessary pain and suffering their food dollars are enabling; most vegetarians, for example, have no idea how much suffering is attendant upon their dietary choice.