4Chan was only ever right about four things
ShitpostingI'm guessing it's because developing a vehicle class for a single train seemed like a lot of work.
We've got people. People are well supported, and the work of other teams will continue testing and improving the people class.
If you make a person look like a train then it'll kinda work, but it's hard to map all the limbs etc into train components. If the train component is a single item, then map it to a person's hat and create a very narrow path the person can run on, exactly the right height below the train tracks. Allow this person to clip floors but not walls.
I'm guessing it's because developing a vehicle class for a single train seemed like a lot of work.
And, given the trouble they had with the cart at the beginning of Skyrim , it's not surprising they went with an easier option for a quick one-off area transition.
Wasn't Skyrim a different set of developers anyway? Bethesda and Obsidian
Fallout 3 was made by Bethesda and that is the game that the train hat/glove(the player can't see worn hats in first person, but they can see gloves) is present in, as it is from the Broken Steel expansion. Obsidian made Fallout: New Vegas and probably used that trick too, but Bethesda came up with solution first.