I'd imagine there are many, but one's probably the fact that we don't as regularly experience it as our ancestors did. We don't behead chickens for dinner, we don't fish the local streams to survive, we don't watch wolves kill baby lambs in our flock. Combine that with our capacity for empathy. Sentience isn't required; I feel bad when I throw away one of my houseplants.
> Can you actually make that claim clear and distinct without waving it away as self-evident?
I don't think anyone's got a perfect handle on what defines sentience. The debate will rage, and I've no doubt there'll be lots of cases in our future where the answer is "maybe?!" The edges of the problem will be hard to navigate.
That doesn't mean we can't say "x almost certainly isn't sentient". We do it with rocks, and houseplants. I'm very comfortable doing it with ChatGPT.