Just like a lot of things where the best thing to do for the individual only works out if only a tiny minority of parasites do it. e.g. getting a vaccine. You'

Just like a lot of things where the best thing to do for the individual only works out if only a tiny minority of parasites do it. e.g. getting a vaccine. You're arguably best off if you're part of the 1% of the population who choose not to get one but still get protected by herd immunity. But if that 1% grows to 10/20/30%, suddenly, not only does the defection advantage disappear, but the whole herd starts to suffer. Tragedy of the commons. We're all stuck between a rock and a hard place of simultaneously not wanting to restrict individual freedom, autonomy, and privacy, but also recognizing that when being a parasite is a disproportionately advantageous role for an individual to choose, it eventually kills the host.