Are you all going to make me do this every day? Turn on your lights when it's dark/grey out, people! It's really not hard. There's usually just a little switch next to the steering column that you flip. Even if you can see, there is no guarantee that someone else can see you.
Unless you really want to die screaming in a fire--in which case, I'm all for it, as long as you don't involve anyone else. Namely, me.