Here's the problem...many of the crack/meth hoes that come into the industry probably don't want to get tested for herpes because it would eliminate them from working to support their habit. And if they didn't have porn, they'd end up on the corner.
As far as the guys, they simply don't care if the girls have herpes or if he has it and spreads it because simply he can't get another job anyways.
It's a vicious cycle but the performers simply have nothing else to do to support them so they choose to live with a STD that isn't fatal.
These performers can live with Herpes because it isn't taboo. 1 in 5 American teenagers and adults have Herpes type 2 and 1 in 4 American women have herpes 2. So based on those national stats, we can apply to the number of performers.
Herpes Stats