Over all, private information can be incriminating, not just in terms of bullying and pedophiles. Let's say mom calls in sick. Kid snaps a picture of her mowing the lawn. Dad has a swastika banner in his trailer. Kid snaps a picture. Dad is quite seriously ill. Kid snaps pictures of him in bed every day.
Privacy breach happens, and employers, potential employers, banks, insurance investigators etc. suddenly have access to that information by name. Mom gets fired. Dad will never teach again. Dad can't get a life insurance because of his current health status.
Some of these scenarios are unlikely, and some of them might seem like net benefits to society if we squint a little. But the breach of privacy was detrimental to people, and we all do things that we don't want everyone or anyone else to know about.