I, too, was interested in the daytime running lights which I believe the 2003 Prious had. I did ask a dealer about it. You are right. They are required in Canada-- and hence, the Canadien 2004 Prius has DRL. However, they eat up your stored energy in your battery. Therefore, if you do not need DRL, the wisdom was, don't use the battery for them during the day.
When I first received the car, I was also told to 1) TURN OFF the light in the truck. (It came to me in the "on" position.) Our mantra is: Minimize the drain on your battery! 2) Turn off the overhead light so that it , too, does NOT go onto automotiive mode when you leave the car. 3) I just found another light to turn to the "off" position: the light underneath your sun visor-- on each side. (I just realized that I have not turned to "off" the light on the passenger side visor.) When you open the mirror, the light "automatically" goes on. Turn it to "off." Most of the time we never need it -- or never look in the mirror anyway.
I think that many of these lights in the "on" mode-- even when they are not being used-- might drain the battery.
Also, I have always started my 17 1/2 year old Toyota mini-van truck with all "appliances" in the "OFF" position. It is kinder on the battery. So, I do the same thing for the Prius: I do not turn on the air conditioning until the car is up and running. Less strain on the battery start-up.
By the way-- I get good mileage. But I have to work at it and "squeeze every bit out. I LOVE THE PRIUS!!!!
Karen Ann