Excellent point. But do we ever lose consciousness, though? Arguably, a continuum of consciousness is what defines us as individuals. If there was an absolute loss of consciousness, you would indeed die every time you fell asleep, but this is never the case. The impression of loss of consciousness is related to the fact that memories cannot (usually) be transferred between different states of consciousness.
Moreover, when you talk about the substrate of consciousness, that begs the question of what consciousness actually is, and how it can be transferred. Creating an exact copy of the substrate (or an exact copy of the data pattern, but on a different kind of substrate), and then destroying the original substrate and crossing your fingers - this is a product of magical thinking on the part of scientists.
Moreover, when you talk about the substrate of consciousness, that begs the question of what consciousness actually is, and how it can be transferred. Creating an exact copy of the substrate (or an exact copy of the data pattern, but on a different kind of substrate), and then destroying the original substrate and crossing your fingers - this is a product of magical thinking on the part of scientists.