In the past times the main thing that went in a cigarette lighter was a cigarette lighter, now'er day individuals have a wide range of thing which they can undoubtedly neglect to unplug which could deplete the battery.
I had a client once who's vehicle battery had gone level on their Rolls Royce, Silver Shadow. It required a long time to discover what was causing the channel. It ended up being a golf ball, stuck between the switches for the front power seats and the cigarette lighter, keeping it squeezed in. I don't recall 'charging' him for the work.