I'd never pay for porn or even food with BTC. Can you imagine 10 years from now? "god dammn I wish I didnt pay for that wank with BTC, that few USD worth of BTC I paid is now worth 100k USD"...
Since many people are very fond of looking at the zest, then porn was always appreciated and was in demand. Of course the cost of this pleasure was significantly high. And the fact that porn takes the opportunity to earn with the help of a crypto currency, a very expected trend.