Because it necessarily violates quantum no-cloning. I think the state of any human at time t is a quantum state, more specifically a linear superposition of n distinct states with probability amplitudes.

I don't necessarily agree with the lookup table analogy - sure, consciousness is finite, but it is also a chaotic system. Else, it would be extremely easy to predict every possible set of actions I will make in my entire life. As Aaronson mentions, I don't think you could do that without killing me using something like Laplace's demon.

It's relatively easy to create a simulation of me - that's merely a problem of data. A simulation wouldn't be conscious though, it would be like me, but not me proper.

I think there is some intrinsic property that gives rise to consciousness, as of yet undiscovered. Hard to say though, after all, are we all not information?