Teenagers actually need almost as much sleep as young children, and they often experience delayed sleep phase (meaning they're up half the night and then sleep until noon). All of this is physiologically and developmentally normal.
Is he fine in himself? Eats well, does well at school, sees his friends? If all of these things are fine, it's probably not a major issue.
My parents used to have a rule at the weekends and during the summer. You had to put in an appearance for lunch. (Assuming you weren't working.) Breakfast was optional.