One reason atheists are wrong about materialism, determinism, and free will

A number of notable atheists, including Sam Harris and Daniel Dennett, accept determinism (and materialism) and argue that our sense of making conscious decisions (free will) is an illusion. Our conscious experiences, they say, are only by-products of material processes. Our conscious experiences are made entirely by our brains, and each process within our brains are, like all physical processes, determined entirely by previous events/conditions and the laws of nature.

But if free will is just an illusion and our conscious experiences and sense of free will are just by-products that are entirely determined, then why would evolutionary processes bring about conscious experiences, and a progressively deeper sense of conscious experience in more advances lifeforms? If they are merely an illusion and nothing but a by-product, then they would have no evolutionary benefit whatsoever.

Sure, one can argue that conscious experiences (including the illusion of free will) are just happenstance by-products that evolutionary processes happened to bring about (despite no evolutionary benefit and greater “levels” of conscious experiences in more evolved lifeforms). But doesn’t the idea that consciousness is fundamental make more sense?