I think it is because this isn't their "real" lives. Real life is Japan. This is "at sea" and doesn't really count. For many, they come here, make the money, and then mentally flush the whole thing, never to revisit it in their minds.
We have seen on the board here, at times, that when "what happens in Canada" doesn't stay in Canada, and starts to cross over to Japan... the door to video (or any contact at all) is likely to get slammed shut in a hurry. Telling a Japanese lady that you know the small town in Japan that she is from, and you visit there regularly, is probably a seriously bad idea

if you want to keep seeing her, with or without video.
It the same kind of thing why you might see a Korean (or whatever) lady put in her ad "No Korean men." They don't want anything crossing over to their "real" world. That and the extended family issue

Don't want to risk that either!
This is for ladies visiting from Japan, Korea, etc., obviously. If someone is of Japanese origin (or whatever), but now lives here... it will be different. If they have another job, kids in school, husband, boyfriend here, etc. etc. those will be huge factors. Everyone is a little bit different.
I can tell you, however, unequivocally and from long personal experience, just because someone doesn't advertise a rate for photo or video, doesn't mean it is not available... at least for some people in some cases. It is mostly trust building.