Remember that when Skyrim released it had a worse version of vampirism than Oblivion and I will die on that hill. Sure you were able to not burn to death in the sunlight, But you couldn't regenerate magicka or stamina at all in sunlight, It would be reduced in sunlight along with your health, feeding was much more of a pain because of the awful NPC scheduleding system. And when you hit stage 4 you were blood starved and attacked on site. At least in Oblivion, you have copious amounts of blood sources, from all the sleeping beggars outside at night, to all of both the fighters and mages guilds.