If you have noticed mainstream TES vampires are good compared to freelance, ones that live in caves. Vampires minus the Volkihar have been minding there own business, until the Dawnguard started to stir the pot.
Example 1: Janus Hassildor even though he is a vampire he sends you on a mission to kill them, because he finds vampires evil and dangerous.
Example 2: Rona Hassildor refuses to feed, for various reasons and would rather die than drink blood and harm someone.
Example 3.: Someone already said this but the Vampyrum Order in Cyrodiil gets rid of criminals, and feeds on sleeping people so, it won't harm them and the victim won't attack.
Example 4: If you join the Volkihar, you get missions to kill other vampires that are considered feral, to prevent them from turning humans and overfeeding.
Example 5: In Dawnguard the vampires took the time to design a potion (blood potion) to replace blood, so they don't have to feed on humans all the time. They still feed on humans though, but that amount must have been reduced due to the potion.
All in all the vampire factions regulate themselves, and enforce strict rules to protect their food source. Violating one of their codes of conduct results in immediate execution.