We don't know that it is still there. For all we know, the North Star or any other star could have been ingested by a passing black hole years ago. (Although this is highly unlikely, it is possible.) When you look at a star, you are looking at the light that came from the star. Because stars are so far away, it takes years for their light to reach us. Therefore, when you look at a star, you are actually seeing what it looked like years ago. It is entirely possible that some of the stars you see tonight do not actually exist anymore.