Its more than just rebelliousness. Teens' circadian rhythms are naturally shifted towards falling asleep later in the evening and waking up later in the morning.
The cicadian rhytm doesn't actually know what the clock on your wall says, only when you eat and get daylight. A late cicadian rhytm is functionally equivalent with poor sleep hyhiene.
And when other people are active. It seems to be fairly common that night owls need an hour or two of their own time after most other people have gone to sleep, or at least have stopped bothering them.