Actually I read something quite interesting on that and saw a SEX TV episode with a gay porn actor who always brought his wife to the shoots and has no physical desire for men, but gets paid very well , and says he is not either gay or bi, has no attraction to men, just viagra and money doing the job.
The same logic applies in California who used to prosecute porn stars for prostitution and for pandering/pimping for the producers. The appeal case hinged on the definition of prostitution which was having sex for money for the pleasure/enjoyment of the client. The porn stars said they really didn't enjoy it at all and they were doing it for the money as actors. Since they didn't meet the definition of prostitution by the lack of intent to achieve pleasure the appeal was upheld and they now are not prosecuted.
Think of a lot of typical sankie clients - the sankie is handsome in his 20's, fit and virile, his client is overweight, smokes 300 cigarettes a day, drinks too much, older by 20+ years, possibly quite ugly, he still gets it up and does the job since it is a job and not an attraction.
Were money not involved they wouldn't do it at all, and a non-sankie might not even be able to perform - no stimulus, no enjoyment. Men in particular need a lot of visual stimulation to be interested and even if I was paid I wouldn't touch a lot of the sankie women I have seen over the years at all.