This is interesting because you seem to have totally missed the significance of computers and smartphones. Your parents would know what you were doing because if you were in the house you were safe. Have you not come across sexting, cyber bullying, internet grooming etc? So your parents knew what you were doing but were not snooping?
As it happens, this teenager wasn't with me when they were younger, but I don't think that is a significant factor. If you see the group chats that go on in skype there are several in their late teens who are talking about underage sex, soft drugs, alcohol, smoking. This shouldn't come as a surprise to anyone, it's just teens trying to grow up, with the exception of the drugs these will all be legal activities in a couple of years time for them.