daydreaming becomes maladaptive when it interferes with someones life for example that 18 wheeler who is driving a "long haul" they begin to day dream while on the highway and bam they crash into another vehicle or swerve off the road over a cliff.. or maybe someone is babysitting very young children and they begin to daydream and get so pulled into their day dream they do not realize those children in their care have figured out how to open the front door and end up down the street either in an accident or lost or in the arms of a stranger...

extreme examples yes but thats what maladaptive daydreaming is, it puts the dreamer and those around them in danger, a harm to their self or others. thats why its called maladaptive.