Because if you do not give them a warning, they may blame you later.
True, its easy for newbie traders even if from your own family to point the finger on you and blaming you for their loss.
It's human nature, buddy. Average people do not research after they get any suggestions. They see how it sounds, and if a suggestion seems good, they will take it without thinking about the possible negative impact. It happens especially in India. Also, Indians are master (Especially west bengals) to blame others for the mistake they made.