Yeah, how would you like it someone knows you better than yourself? Image a guy walk up to your house and tell you everything he knows about you, height, date of birth, social insurance number, education, final marks in high school, bank statements and you dont even know this guy's first name.
Also, people can sell your personal information for a large amount of money. This would lead to identity theft, commercialism in your face 24/24.
I dont want anyone to know about my personal life.