And this assumption has only gotten more common in the ~56 years since (so the anecdote goes) ELIZA fooled Weizenbaum's secretary.

"Consciousness" has ~22 different definitions; some are easily met, some are not even met by the humans giving those definitions (for example, I've seen people here on HN who write as if consciousness can somehow magically solve the halting problem).

There's only one test for it in AI, that I've heard of, and that I think is worth exploring: https://www.youtube.com/watch?v=LWf3szP6L80

It has to do with the fact that all our definitions of "sentient" and "intelligent" are extremely vague, often vacuous, and generally boil down to "I know it when I see it" in practice.

So there should be absolutely no surprise that, when something comes along that behaves in certain ways very much like a human (and unlike anything else), it is assumed to share the basic qualities of such. It is how we judge other people, after all - it's not like you do a brain scan to determine whether someone you are talking to is "sentient", whatever that means to you. You judge that by their behavior, modelling what a "sentient" would do and comparing the result to what they actually do.

I suspect this has to do with how shallowly people even regard their fellow man. To the point that if the outputs of an entity parrot humans well enough then, well, there couldn't be any differences whatsoever, and it must bear all the titles which we gift to humans.