Some people don’t dream because of medical/biological issues, if you do certain drugs like smoking weed it greatly lessens your chances of dreaming. Dreaming only happens in REM sleep which takes hours of sleeping to get to that stage. Dreaming isn’t guarenteed, and most sleep is not dreaming sleep.

I e been under anesthesia before and it’s exactly as you describe, one moment you’re awake in the room and literally the next moment you’re waking up from surgery. It’s a very unsettling feeling not being to account for the lost time