Despite, perhaps, all your experience to the contrary it's only a relatively recent change to a situation where "most people" have no association with the animals they eat for meat and thus can find themselves "not thinking about it very much".

It's only within the past decade or so that the bulk of human population lives in an urban setting. Until that point most people did not and most people gone fishing, seen a carcass hanging in a butcher's shop, killed for food at least once, had a holiday on a farm if not worked on one or grown up farm adjacent.

By most people, of course, I refer to globally.

Throughout history vegetarianism was relatively rare save in vegatarian cultures (Hindi, et al) and in those cultures where it was rare people were all too aware of the animals they killed to eat. Many knew that pigs were smart and that dogs and cats interact with humans, etc.

Eliezer was correct to think that people who killed to eat thought about their food animals differently but I suspect it had less to do with sapience and more to do with thinking animals to be of a lesser order, or there to be eaten and to be nutured so there would be more for the years to come.

This is most evident in, sat, hunter societies, aboriginals and bushmen, who have extensive stories about animals, how they think, how they move and react, when they breed, how many can be taken, etc. They absolutely attribute a differing kind of thought, and they hunt them and try not to over tax the populations.