Because they don't have any other higher level function that could reason about the state other than a single binary response. If intelligence is a continuum yo

Because they don't have any other higher level function that could reason about the state other than a single binary response. If intelligence is a continuum you might say it is at the lowest end (a bit state and actuation on that state). But consciousness seems more like a meta-intelligence that would require more than one bit and one actuation.