Well, first, the comparison you're drawing between something created by nature and a machine designed by us as a tool is incorrect. We were not designed. Its not that "nature" did not aim to create consciousness, its that nature does not have any aim at all.

Second, our very being is fundamentally different from what a computer is. Experience is a core part of being alive. Intellectual function is built on top of it. You're proposing the same could work backwards; that you could build experience on top of cold mechanical calculations. I say it can't.

Part of the reason is the hardware computers are working on, they are entirely digital. They can't do "maybes."

Another part of the reason is that computers do not "get together" and have their unconsciousness meet. They are calculators, mechanically providing the answer to a sum. They don't wander, they don't try, they do not do anything that was not a part of the explicit instruction embedded in their design.