oooh i think it's because we don't really see how it happens from inside of the elevator... but i am not so sure.
there was a period when i only got dreams with elevators. at first the building i was in was just the apt building i lived in at the time, but as dream progressed it looked more like a toy house built out of fabric patches. what patch blanket looks like - that was what i saw on each floor. the main problem of the dream was however that the elevator arrived at random floors. i press 7, it arrives at 117. i press 117, it goes to 49. i press 1, i see floor -16. and that was an endless loop. i never arrived at the floor i needed in any of those dreams, even a couple that i saw out of that period.
the only time where an elevator in my dream functioned differently to that was my second nightmare in my life :((( when it was supposed to arrive it didn't, but the doors to the shaft opened anyways, and my dad walked in without looking. it was 7th floor. the dream cut off there.
but with ladders idk how to explain it. but yeah some missing steps sure did appear in some of my dreams, the less than incorrectly working elevators.
OH. idk about you but in my dreams there're always some complications! i never ever had a dream that was 100% good. there were some dreams that were good in contrast to complications or because i overcame them or the complications were so interesting the made the dream into a film, but never had i a completely smooth dream! so i guess, at least in my case, that faulty ladders and elevators are possible mandatory complications