Cannabis affects short term memory and for that reason we tend to wake without memory of dreams.
This does not mean that we do not dream.
Further, for those bothered in dreams, it is nice to wake up without memory and ownership of 'bad times'.
Minds create dream worlds from our memories, desires, and knowledge. They may be worlds of vast grandeur or dungeons of dark desires.
Upon waking, everything, everyone in that world goes away without littering the bed with their imagined rubbish.
We are each simply 'conscious-being', there when awake, there when dreaming, and there in deep-dreamless-me-less sleep.
I personally have no need to mix the real world with my personal world and worry-not about dissapearing just because worlds go away.