Certainly I think its nature as an extreme, edgeplay sort of BDSM puts it on a no-go list for a lot of producers and releasers, but I'd also argue that it probably has a lot to do with the pretty outrageous cost of the equipment and finding and paying people who are trained and knowledgeable about using them safely. A website is constantly putting out material and getting instant purchasers to fund those costs (or, like for Kink and Twisted Fantasy, are big enough that they can go ahead and produce it without fear of losses) ; DVD's require somebody to front that money in the hopes that it will sell well.
I'd bet as well that there's a concept that fetishes like electroplay sell better in online on-demand format anyways, since the people who really want it will look for it on the Internet, and vanilla folks will ignore it on the shelves.

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