Explanations as to Why My Neighbour's Upstairs Light Is Always on, Ordered in Increasing Paranoia

And I mean always. ALWAYS. They live across the back lane from me, and I'm pretty sure it's a bathroom because the house seems to have the same layout as mine.
  1. It's not actually always on, I just so happen to only see it when it's on
  2. They forget the light on every night
  3. It's a super powerful night light
  4. Their light switch is broken
  5. They have a phobia of light switches
  6. They are really afraid of the dark
  7. It's a tanning bed room
  8. It's a marijuana grow-op room
  9. They are awake at night only, and hangout exclusively in their bathroom because the have very bad gas
  10. It's an Easy Bake Oven room
  11. They are attempting to break the world record for longest lit light bulb
  12. It's the only source of heat in the house
  13. It's a mythical light switch and you must sacrifice a finger every time you turn it on/off
  14. They died, they're bodies are rotting away, and they are just racking up the electric bill
  15. The light switch for their bathroom is hidden somewhere inside my house
  16. They are hiding from a bloodthirsty monster that fears only two things: bathrooms and light
  17. Whatever was in the pulp fiction brief case is being stored there
  18. Thomas Edison has been trapped in there for decades and is signalling for help the only way he knows how
  19. They are up all night making sure the demon that lives in the toilet tank doesn't escape and eat their children
  20. They are the Guardians of Light and if it turns off, all light bulbs around the world will explode and kill everyone
  21. It's an art installation
  22. It's a distraction window and they are watching me from another window
  23. It's me watching myself from a parallel universe that exists inside the house but I'm invisible to myself