Also a matter of purpose, killing animals for food is more acceptable than killing them for sport or entertainment

Exactly this. Meat is a huge source of nutrition. Even though in our modern western society, we might not "need" to eat meat, but it's a hearty, plentiful, accessible protein and fat that stores well and can be easily moved and replicated quickly. It's simply much more practical still to keep eating meat in much of the world. I'm not going to go into the arguments about our biology either, but I think it's safe to say that our bodies are also very finely tuned to eat and process organic (from organisms) meat and use it as fuel. Sure, you can feed your cat a vegan diet or whatever and replace all of the vitamins, but there is no denying that the more "natural" way would be to just eat the meat and be done with it.

Many of the arguments for veganism come alongside ideas for better animal welfare, but the two are not mutually exclusive. The only reason we don't eat grandma after she dies is because it's culturally unacceptable. We can apply more respect and reverence to meat production without stopping entirely or pretending that the benefits of eating meat don't exist.

In the developed world and large parts of the developing world, meat is consumed for entirely hedonic reasons (ie. for pleasure). I would not consider this materially different from killing for sports or entertainment.

One could say the same with slaves: slaves for work are more acceptable than for fun.