[polishdude20]

I wonder if this is heavily based on the fact that during sleep, all inputs are shut down. Like, you can't hear, you can't see, you can't feel, no smell, no taste. All senses to the outside world are off.

What is it about external inputs that makes the brain not be able to do it's sleep "duties"? Is it that external inputs take up processing power that needs to be used during sleep instead?

[funnym0nk3y]

But that's not true. The senses are not off as you wake up when light increases, when there is a loud sound or when there is a stron smell. In addition there are numerous examples that the sound of the alarm clock gets integrated into the dream, maybe as a telephone sound for example.