I think the intended audience for shit like this are guys whose sex life is limited to watching porn. Every once in a while they get to a point where there feel like they've seen it all and need something different then mainstream porn can offer. That's why there is shit like scat, foot fetish or "the messy girls" produced.

Of course, there are some whores who simply like doing the weird shit. Remember that happy smile on Veronica Jett's shit covered face?