It is because the dominant, publicly acceptable scientific paradigm (especially among journalists) is rational determinism. Among its 5 key assumptions is that mind is an epiphenomenon arising from matter. Thus, many people believe machines made of matter may gain consciousness. The other thing is that as a culture we are trapped by a broken metaphor that the brain is a bio-based computer. [Hint: it is not.]
Consciousness is fundamental, not matter.
Thank you for stating something that should be obvious, but (weirdly) isn't
@TheAtlantic