they couldve put anything like the activation needs a biometric reading or a blood or literally anything more than
just "uhhyeah it HAS to be you because uhhh reasons and stuff"
They ruined my boy Charon. You don't really know much about him, other than that he was brainwashed as a child and he has to do ANYTHING that the holder of his contract tells him to. That's why he kills Ahzrukhal only after you buy his contract from him, no doubt over all the nasty things he had to do because of him that he didn't want to do.
So, how does that translate into the actual game? Well, if you want to hire him when you have another humanoid companion, he tells you he doesn't feel like going with you, and he decides to bum around in the 9th circle, where Ahzrukhal's body is likely still rotting away in public. What about turning on the purifier at the end of the game? Well, if you have Broken Steel installed, he has a brain blast and says he just realized he is immune to radiation, so turning on the purifier won't be an issue at all. If you don't have Broken Steel, however? Well, he tells you to piss off because "this is not part of the contract". Okay, buddy.
Quite an interesting character ruined by the game he's in. Shame, he's the only human companion that follows you no matter what karma you have, so he's the most accessible, and the most interesting companion in the game.
The whole plotline of Fallout 3 is fucking stupid and full of holes, so looking for one particular plothole is an exercise in futility when there is another one waiting right around the corner. I mean, the story is centered around a water purifier, but then any character in F4, even those with 1INT can just build a whole bunch of them at level 1 in Sanctuary. Smaller scale ones, of course, but it's still the same principle. Why the fuck were these chuckleheads in DC having so much trouble with this, again? BTW, in the real world, you can purify water with just some sand.