I think thats because skyrim is a different strain but hey at least they get weakened in the sun instead of just sparkling I would take weakened over sparkling any day.
Well, I stand happily corrected with knowing fangs are in.
Yeah, I know, different strain and all. But I have a feeling vampires might not get sun damage at all next game.
Morrowind: Constant sun damage.
Oblivion: Constant sun damage, when fed, however, you can walk in the sun unharmed for a single day.
Skyrim: No sun damage, but character is weakened.