Given that this is the Newbie Corner another point of view while we're in the dark if the bulb (i'm sorry) is 5V or not. For the newcomer (totally not happened to me, of course, i would never....
) the physical separation of mains and the circuit is not as immediately clear as it appears. The voltage has to be dropped down, fed to the individual components AND mains of course has to continue to go to the (i assume) mains consuming device. I know that sounds ridiculous and i'm not insinuating OP thought that, its just a mental roadblock i totally not remember having had ever
If I were to guess why anyone would think that it's a leftover from the expectation that a electronic device is an end point, that you are closing a circuit sounds easy on paper but doesn't immediately transfer. You think you plug it in the wall and that's it. Again, not insinuating anything, it's just probably reasoning that is so far removed from experienced peoples' way of thinking that it actually may help someone. Or make me look stupid. That's fine too