I suspect the attitude is the default / most primitive one, because any other attitude requires higher-order cognitive processes that can abstract one's own experiences (which is the only real input one has) with the behaviours of entities that appear to be very different from oneself. In other words, the capacity for empathy is a "positive feature", in the sense that it is absent by default.

The ability to make this kind of abstraction is a pretty sophisticated thing, and either requires time to evolve (as an instinct), and/or requires socialization/learning (as a partly or totally-intentional practice).

People don’t like it, just like many people don’t like animals being aware.

I had a fascinating theological discussion with a guy once. He was a farmer and he believed strongly that animals lack souls. I, on the other hand, believe that even amoeba have souls. I feel it’s just a condition of being a living thing while he felt that this was unique to humankind. Obviously, he has an interest emotionally in viewing animals as soulless. Easier to slaughter them that way.