Imagine walking through the city with only the street lights illuminating the roads? The city would be a dark and scary place. The cities leave their lights on to give a welcoming feeling to visitors and tourists. I agree though, some buildings seem to have every light on, just for the heck of it.In Australia, buildings are required to turn off lights that are not security risks or have no other purpose, during night hours.I suppose tall buildings leave their upper floors lit because small planes and helicopters might fly into them, not seeing the building. Some buildings use the upper floors as apartments, Penthouse Suites. Many buildings are being converted into apartments whereas previously, they were offices, and tenants are the culprits.
Almost everyone is going to say security purposes, so if someone breaks in, they can see them better on camera.