Because of the difference is that there's a hard cut in continuity with the teleporter. The body is destroyed. In normal life, our body does get replaced, but the continuity remains equal through that time. With the teleporter, everything gets replaced at once, which is a hard continuity cut.

For this reason, sleep doesn't affect continuity, just its potency and what can be accessed during sleep. If we turn a microwave off by unplugging it, whatever continuity it has ceases, this is in no way equal to sleeping. The functions, information, and mind are still present and functional.