I've had the same question myself.

We've acquired and viewed videos over the years, and have usually been disappointed. Too many bondage videos focus on the ropes and bindings, without any actual sex -- and the faked sex in some of these film is pretty poor. Films with lots of sex may have some BDSM elements, but it tends to be rudimentary and silly.

I suspect there's some law in the U.S. about mixing BDSM and sex in the same video.