DRL's are there to increase safety, i.e. oncomming road users can notice you further away, therefore less chance of one overtaking and hitting you. If someone is behind you travelling in the same direction at roughly the same speed then they should see you without he need for DLR's, otherwise they need a white stick and should not be driving! In some European countries it was law to turn on side lights during the day if you were driving on country roads i.e. roads through wooded areas, to increase your visibility and therefore increase overall road safety. This is just an idea that has grown from there. It is a safety issue and not a cosmetic one, believe me they are bright enough, I see loads of new S-Max's driving around Germany as they are a favourite with married British Soldiers, and you can see them a LOT easier than other vehicles without DRL's.