DRLs must be switched off at night as they would cause bad glare to other road users (they are noticeable in the daytime by causing glare when it doesn't cause problems).Iv asked this question aswell, don't know why the 'Halo' led ring goes off with the side light being on !!!!
"But I don't mind causing glare to other people if it makes my car look good" is not the public-spirited answer.
I guess lots of people think DRLs are just a fashion statement and not a light with a purpose.