But they never seek out bi porn. They seek out gay porn when they want to be gay. They seek out straight porn when they want to be straight. They veer uncontrollably from straight to gay, to straight again. I can only think of two bisexual men who actually seek out sex with a man and a woman at the same time.
Markets require supply AND demand.
The demand's just not there, sadly. I've seen some bisexual porn coming out of Europe. Rather, I'm aware of bisexual porn in Europe. All Worlds has some bisexual porn coming out, but it's mostly 10 Czech men gang-banging one woman.