Nina Dobrev leaves 'The Vampire Diaries' tonight. Here's why that's a big deal.

On Thursday night, Nina Dobrev will appear in her last episode of "The Vampire Diaries," the hit CW show she has starred in for six years. To a lot of people, this is a very big deal.Then, just as many people have no idea what that means. Who cares if one actress is leaving a show?