Are steam cleaners supposed to leave streaks that will 'go away' later?

My dad rented a steam cleaner thing for the carpet and used it on the living room and hallway. It left the floor looking really streaky but he keeps telling me that its just because it's wet and it'll dry. But it's been a while now... will the streaks really go away or did he do it wrong? Honestly our carpets looked better being consistently dirty than it does looking half dirty half clean.