Useful to animals who evolved it. I have no more control over my individual neurons than an adder circuit has over itself. And this extends, layer by layer, all the way to the external actions I take. I don’t really control my inner dialog. I don’t really control what I say or do. There is a biochemical process which makes it all happen and I exert no power over.

But what is useful about this “illusion.” In a purely deterministic world, any sense of illusion is completely irrelevant. You might as well say “pebbles on the beach don’t really have a sense of community, it’s just a useful illusion that they share.” It’s just as arbitrary.