We dislike porn stars, sluts, hookers, prostitutes etc. because the specialness quality of sex is removed. Most things revolve around this ‘feeling of specialness’. There is a whole spectrum we use to evaluate. For sex with an ordinary girl, we would like her number of previous partners to be between 0-10. Once it gets much more than that, the specialness factor is drastically reduced. Say she has slept with 100 men and you are the 101th person. Your relative value is 1/101 vs. a virgin who would make your relative value an absolute 1. That’s why virgins are rated so highly because they give you the highest ‘special’ value. You are their first experience and its incomparable for them. First experiences are special because their relative value is the highest.