observations in a tokyo cinema

In all other places where I've been to a movie theater, as soon as the credits start to roll at the end of the movie, lights slowly start to switch on, and people start to leave their seats. Only a few movie buffs stay to watch the credits.
Well, not in Tokyo. Here, the room stays dark until the very end and people wait until all the credits have passed. Only then the lights switch on. The few people you notice leaving the theater earlier are most likely foreigners. Ninety-nine percent of the audience stay put in their seats.
As somebody used to leave the seat as soon as the movie ends, it's kind of unnerving having to wait, even if only for a couple of more minutes, until the credits are over (oh, the stress of modern life). I take this extra time to observe...they all seem to pay close attention to the screen.
Why the difference in behavior?
Is this a country of movie buffs? No, probably not.
Do people feel that the credits make part of the movie experience?
Or is it a case of politeness? For other moviegoers, for the movie makers...
I have yet to find the answer but this is certainly... hmm, different. But very interesting nonetheless.