system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do unoccupied houses fall apart?

Why is it that, in houses left alone, things like the stairs rot and fall in?  As opposed to houses where people walk up and down the stairs all the time, but don't have to constantly repair them?
gpt
Wood in old houses left alone won't rot on their own.  They need stuff like broken windows to let in moisture, burglars to steal the copper pipes and get stuff wet, and melting snow that has blown in.  A house that is well sealed from the elements will not rot. 

Unless, of course, the ghosts are pee-ing on the stairs!