I've been into it for a number of years now. I'm a leg man. What got me into it was sifting through galleries and galleries of leg and pantyhose pics...and I came across something labeled Japantyhose! INSTANT boner. Started searching for more until it snowballed into the awesome obsession I have today. It's a love story, really. Haha!
But to adress your question...it certainly isn't mainstream since we get bombarded with porn out of California and wherever else they make it here in the States (if you live in the States) and I would assume most of the younger porn dwellers out there want the fast hot f*ck me baby kind of stuff and they don't bother with actual beautiful kind looking and sweet natured JAV actresses. Plus they like 32 minute clips in HD from porn sites and see JAV titles as SD and actual "movies". They probably see them as a bore. Just my opinion. But they are missing out, I'm sure you'll agree.