People with money that dont mind paying for quality content/product.
Same as I pay for a monthly cable subscription, I buy movies on-demand, pay for netflix, go to the movies, just bought some movies on itunes for a recent trip. I can probably get all this shit for free online if I want, but im not cheap and I appreciate a quality experience. The causal porn consumer is gone, but people who are porn connoisseurs or addicts will keep paying for porn.
Ill put it in terms you can related to. You can get high off dustoff or sniffing paint, Laird's Vodka or Mexican dirty weed for almost next to nothing, but you pay for good drugs and booze because it is a better experience and a better high. A drug addict is no different than a porn addict. Both need their fix of the best possible product if they can get it.
