is it saving or wasting?

Okay so this is probably a ridiculous question, but why do people leave their lights or TV on all day long?, it is almost like they do it on purpose, I see it everyday in some houses, it is almost as if they believe that it will save them some power and make their bills lower, I actually started to wonder if it does,
Maybe it does, I can't be for no reason, or is just extreme irresponsibility?.