Who's they? Farms? Whether they be factory or private farms, there are many that kill animals less than humanely.
Who here has been to an actual slaughterhouse to see them butcher your normal domestic farm animals like cattle and pigs? They don't humanely inject every animal and put them gently to "sleep" before butchering them. It's .22 caliber to the head, drain the blood, and divide them into cuts of meat. You'd hope they're brain damaged enough not to feel everything, but they're definitely not out instantly. I don't think this is how it should be, but that's how it goes.
But I think we both agree were the biggest sufering is