Yeah, I noticed that last year too. Most people just don't even turn on their lights in the first place, that is why teh change is really not dramatinc at all.
+ after earth hour people just keep their lights off, so there is no brightening effect either. I went to the concert at NPS last year, and it was really awkward, because Miller flipped the switch, and the City Hall light went off, and nothing else happened. People were starting to boo, especially because FCP had literally every single light on. Then like a minue later, all the FCP lights went off. Now that was an amazing sight.
Although it's obvious they purposely turned all their lights on before Earth Hour, so that when the time came, they made a drastic statement.