Plants seem to survive quite well without consciousness.Consciousness has a survival value over unconsciousness.Why does consciousness exist, and how was it selected for in generation after generation, in species after species (if it is supposedly not causally efficacious, as many people erroneously claim) are good questions that should be asked often.
In any case, since you (naturally) didn't address either of the questions I noted, I'll point out that consciousness cannot be selected for unless it has an effect on the organism, i.e., unless consciousness is causally efficacious.