You dismiss the idea too quickly. Consciousness may be necessary in order to function more effectively and to respond better to the situation. An animal with no consciousness responds to perceptions. An animal with consciousness can respond to realities that lie beyond its perception. That gives the animal with consciousness an advantage.
As an example of a reality that lie beyond perception, consider an animal which perceives another animal. In order to plan its own movements, the first animal must estimate what the other is perceiving, and predict how the other will respond to its own perceptions. The first animal may even have to make multiple predictions of the other’s response and plan it movements according to each prediction. It may even have to include that the other animal is observing it and making its own predictions and planning its own responses.
To respond optimally in this situation, the animal must be able to distinguish between its own situation and that of another. The animal must be able to distinguish between its perceptions and the reality of its situation. The animal must be able to make multiple predictions regarding its future situation, and plan its movements according to each.
It may be that introspection and self-awareness are necessary, or at least efficient, in order to perform these higher level functions. Perhaps awareness of self makes it possible to be aware of other selves and to function more effectively with them. Even by oneself, self-awareness may be a key to envisioning the self in different scenarios and planning for different possible future situations.