Does a 6 month old need a night light in their bedroom or does being scared of the dark come at a later age?

Light not needed. A 6 month old baby doesn't need a night light. However, if the baby has trouble going back to sleep by himself, and seems to do well with a night light, there is no harm in using one in that situation. Also, a night light may help parents see inside the room if they have to go in to check on the baby.
Be practical. Once a baby is born they become visual.Being able to orient themselves (know where they are) can be important to their comfort, and newborns to middle childhood may become disoriented if they wake up in a completely dark space. A low intensity night light is,to me, the humane way to deal with natural needs. If they want to turn it off when older, its their choice.