Why would people go to a unconscious stage while sleeping?

Answer 1

It's simply a part of the sleeping process. As you delve into REM (Rapid Eye Movement) sleep, the non-vital functions of your brain go into rest mode because they aren't needed while you're sleeping.

Some people can keep their mind awake while their body goes to sleep. That way, when they dream, they can control it and experience the dream as if it was reality. This is known as lucid dreaming.