Why There Are No Ladders in Bethesda's RPGs

IGN sat in on a QuakeCon panel discussion hosted by Bethesda's Todd Howard, during which the designer explained why ladders have never made an appearance in The Elder Scrolls series, Fallout 3, or Fallout: New Vegas.
"Play our game; find a ladder that you can use. We don't have them," he said.

Howard explained the primary reason for not being able to include ladders into environments is due to their engine, saying ladders caused problems for character AI.

"One day, we tried to figure out why we wanted ladders so bad because we don't really need them. It just felt like we're game development pussies because we can't do ladders."