Backing up Timo's statement, the new system that was discovered - Wise [a short list of numbers], its location, from our perspective, was obscured by galactic dust. Its discovery came about by a detailed examination of images over a span of time, decades in this case, that showed that there was something moving across the night sky. I think one of the lessons to be learned from this new discovery is that nearness to the observer doesn't automatically apply to knowing that something is next to you. We discovered the nearest systems in the past two centuries, which means that for thousands of years humans didn't even know there was an Alpha Centauri, a Proxima Centauri, or a Barnard's Star.
Well, one of those stars you chose isn't the best example to make your point. Alpha Centauri, being the brightest star in the constellation Centaurus, and the third brightest star in the night sky, has been observed since prehistoric times. Of course, it wasn't known to be really a binary star system, until the 17th century.