Because it's awesome, that's why. A side-scrolling endless runner (aka "free runner") that borrows its formula (if not its dystopian plot) from the likes of Mirror's Edge, Vector grips you from the first frame of its dramatic opening movie.
You're a drone. A faceless, mindless worker among millions of the same. Big Brother is watching. Suddenly, you can take no more. With an anguished cry you break free of your workstation, dash down a hallway, and crash through a window. Careening through the air, you land on a rooftop, where begins your endless run toward freedom -- with enemy agents in hot pursuit.
All this setup feels like one part "The Matrix" and one part the intro from "Mad Men," as all we see of your character is a black silhouette. It's all very stylish.
As you run, you'll need to swipe at just the right times to jump, accelerate, and perform various special moves. The action is incredibly fluid, which is on purpose: Vector draws its inspiration from parkour, the art of running, jumping, climbing, and tumbling in a continuous, fluid free-run.
As you progress through the levels (which get very challenging very quickly), you collect coins you can use to purchase additional moves. (You can also buy coins outright, in-app, using real money.)
Like a lot of endless runners, Vector can get a little repetitive, to say nothing of a little frustrating. However, something about the game -- the speed, the story, the beauty of the visuals -- keeps me going back for more.
There's an expression: God is in the details. And I think that's the draw here: Vector puts enough great little twists on the tried-and-true formula that it comes out a winner.
If you've found an endless runner you think is even better, or you think I'm wrong about Vector's awesomeness, tell me about it in the comments.