Why didn't the Hogwarts portraits ever see any of the crimes going on during Tom Riddle's days? Or any criminals in particular?
We see many of the Hogwarts portraits interacting with students and staff members alike, and some portraits even criticize some of the actions that those students and staff members did, like Harry Potter's and Severus Snape's Lumos in the Prisoner of Azkaban. Also, the Headmaster portraits aid the current Headmaster in their duties by sharing knowledge and information to the current Headmaster, as Dumbledore, Snape, and McGonagall did.
The crimes that Tom Riddle, his friends, and, later, his followers committed could've been reported by the Hogwarts portraits to the teachers or Headmaster Dumbledore. Is there a canonical and logical reason from the books or JK Rowling herself that the Hogwarts portraits never reported a single crime to the teachers and Headmaster Dumbledore?