Valid point, it sounded nicer in my head. I can't imaging they would make a hell pylon though... Anyone living there would be in constant danger from Bone Serpents. NPCs die surprisingly quick.Admittedly I feel like letting NPCs use pylons would be way more of a mistake than it sounds like. With enough pylons (like half a dozen), you'd have no idea where anyone is at any given time. The Guide would probably end up in hell and summon the wall of flesh on his own and shut the pylons down for a week.
And, on that note: Pylons need living NPCs. If you only had 2 down there, and one dies from a sneak attack from an imp, that pylon goes down... Which would be infuriating.