system
A chat on subreddit /r/NoStupidQuestions
human
Yet octopus and squid are fair game despite them being one of the most intelligent creatures on the planet.

Pig is fair game despite being smarter than dogs and biologically similar to people to the point we practice anatomy on them.

Rats and mice are fair game despite being so intelligent we use them in studies to analogue human behaviour. 

I honestly think it's about how endearing our culture views an animal. Rats and mice are "icky" pigs are "dirty" and things with tentacles are "weird". But deer and bear are like Bambi and Smokey.
gpt
You’re not wrong. I think it has to do with centuries of domestication and food use creating a cultural norm of eating/killing certain animals. 

Domestic pigs, cows, goats, and sheep have a millennia of history as “consumption animals” - we’ve bred and raised them to be consumed for so long, that it just seems normal to continue this practice.  Same with rats/mice/rabbits - sure, they’re cute now that many countries live in a post-starvation society, but centuries ago rabbits/mice/rats literally caused famines, malnourishment, and starvation on a grand scale. 

Similarly, wolves/deer/wild birds are still more or less wild - our post-starvation cultures sees them intrinsically as “not necessary to kill”, so hunting strikes a nerve as reckless, cruel, and oddly sadistic/selfish. I mean…we have loads of cow, pig, and other domestic “animal meat”…so why kill other stuff? (In truth, deer are often invasive, and need to be reduced in population to avoid ruining their habitat)

As for octopus/squid, nearly every East and Southeast Asian country eats these intelligent animals on a grand scale, for all sorts of daily meals. Octopus/squid in western diet is still considered moderately “exotic”, but any E/SE Asian household will likely make squid balls, grilled octopus, squid pancakes (think savory flat fried bread with green onions and squid parts), eel, and other “wiggly sea meat”.  I believe there are “fisheries” where these animals are farmed, but don’t quote me on that.

I think that’s also why most cultures with a strong dog/cat culture are horrified at the practice of eating dogs/cats - pigs and cows are of similar intelligence to dogs, but we easily eat one and cuddle the other. I chalk that up to a millennia of human/dog-cat symbiosis, where both animals have an almost genetic familiarity to most humans.

It’s interesting to imagine a retroactive change wherein humans bonded, trained, and domesticated octopuses, eels, and other “non modern” animals. Imagine people walking land-bred octopuses, making YouTube videos with their “cute furry land eel”.