Some of these arguments would apply equally well to the Warlock class. Why would anyone sell their soul and sign up for eternal damnation for some powers?
True. But warlocks have flexbility in their RP. Some warlocks are drawn into a pact because of a deal someone in their family made with a devil, and they don't have a choice in the matter. Some warlocks have patrons that aren't even aware of their existence. or if they are aware, they may not care that there is someone out there using their powers, and want nothing to do with their warlock.
While with the parasite, the game straight up tells you the thing is eating your brain. Taking something of you that you won't get back, etc.
