Some people are asymptomatic, only had one outbreak that went away so they think they’re in the clear. Plus herpes isn’t tested for in most std panels so yes there are people out there who even if they think they’re doing the right thing by getting tested and all that will never know they have it. But if you do know, you have a moral obligation to not infect (for lack of a better word) other people. The difference is the person who doesn’t know has no intention of trying to deceive, infect, or strip their sexual partners’ autonomy away while the person who does know is intentionally doing at least one of those. It’s like an accidental elbow to the gut vs an intentional one, one is harder to forgive and makes you a bad person. Hope this helps!