By the way, how can anyone be sure that the conversation is fully private or not? Cause I use whatsapp and haven't noticed any invasions of privacy yet.
WhatsAp uses end-to-end encryption, which means that only you and the person you are communicating with can read the contents, and no one else, not even WhatsApp. Maybe that's why you did not feel the invasion, and maybe there was no reason for anyone to invade your life)