> In science, the use of anthropomorphic language that suggests animals have intentions and emotions has traditionally been deprecated as indicating a lack of objectivity. Biologists have been warned to avoid assumptions that animals share any of the same mental, social, and emotional capacities of humans, and to rely instead on strictly observable evidence. In 1927 Ivan Pavlov wrote that animals should be considered "without any need to resort to fantastic speculations as to the existence of any possible subjective states". More recently, The Oxford companion to animal behaviour (1987) advised that "one is well advised to study the behaviour rather than attempting to get at any underlying emotion".
https://en.wikipedia.org/wiki/Anthropomorphism#In_science
After years of casually observing stray cats, for example, I would nearly bet my life that they experience complex emotions like love, embarrassment, and depression, but I know better than to draw that conclusion around my biologist and zookeeper friends. While the scientific motivation makes sense somewhat, I think it's pretty clearly a feel-good default notion that allows us humans to keep eating, experimenting on, and otherwise subjugating animals for our own purposes (not that I'm not guilty of some of these).