What's the point of creating anticipation when they KNOW they're going to be cancelled? That seems to serve no purpose other than to piss off the viewers they do have.
I'd like to think that most viewers aren't so quick to anger. Having a story cancelled without resolution can be disappointing and frustrating, yes, but those emotions can be handled more constructively. Often, if a show is cancelled without resolution, it can fire the imagination of the fans, make them keep it alive in their minds as they imagine ways it could've been resolved, write fanfics that continue the story, etc. For people to whom fandom is merely a passive process, absorbing what's fed to them, getting no resolution can be frustrating and angering because they have no way to cope. But for people who actively engage their minds and their imaginations, who understand that being a fan isn't just about being a couch potato but about embracing a fictional world and engaging in it with one's own creativity, an unresolved cliffhanger can be an inspiration. Conversely, if a show wraps everything up and leaves its audience with nothing to wonder about, the audience may eventually lose interest, stop thinking about the show and move on to something else.
It's an ancient show business axiom: "Always leave them wanting more." It's good if your audience wants there to be more of the story than what you've shown them, even if you have no plans of telling any more of it. Because if they continue to be curious about the fates of the characters after the story ends, then they will keep the story alive.