From a locked thread that was requested to move here:
With that said most of the fault lies with the devs. They never properly explain the mechanics of being a vamp in TES so most people end up dying from sunlight when they can easily avoid that. Thing is they don't know how...
Talk to people. In Oblivion, it was pretty easy to get info for what to do by simply going around and talking to people, and you'll find someone with a topic "Vampire Cure". Chapels are a particularly easy place to find help. This is an RPG, not a fighting game, you shouldn't need a popup to say when to do something that doesn't involve bashing skulls.
More power yes, going out in daylight? no. So if you don't drink blood you can't go out during day, only at night.
If you feed and get more powerful, then you shouldn't be able to go out in daylight. You're acting like a predator, so you should be more like one. Act less like a predator and you're not so restricted (but at the cost of your enhanced abilities).
That would make playing vampires way too easy. Like it was said, you have to be forced to feed.
You'd need to feed to stay strong. Don't feed and you get weakened (more-so than normal), which hampers your combat ability and makes it easier to die, but also easier to function in society.