Sometimes people get out of bed and walk or do other tasks while remaining asleep. why don't they do this while they are dreaming?

It is a type of behaviour the correct term is REM behaviour disorder, people who had this kind of disorder act out their dreams. Some move their limbs or even shouting, screaming, hitting or punching.  This also used as a defense of committing murders while sleep walking. 

think its caste system

explanation:

because he is that the right