I was brought up by my gran who had no sense of a need for privacy. When I was a teenager she would walk in on me when I was bathing, getting dressed, etc. She seemed genuinely confused when I started bolting the bathroom door and got mad when I put a catch on my bedroom door (there was no lock and the door wasn't strong enough to fit one).
We had a blazing row over the issue when she walked in on me and a friend changing to go swimming one day when I was about 17. But I only really got my own privacy when I moved out in my final year of university.