It's puzzling indeed, but I think it's simply a matter of how technologically juvenile humans are. We've remained within our own solar system for our entire existence. That means that other civilizations in the galaxy would need to stumble upon this one star in 100 billion in order to find us. I say that even if life exists in a nearby solar system, our methods of observing the universe are far too rudimentary for us to notice. We still have to theorize about whether Mars or Jupiter's moon, Europa ever had (or have) liquid water. Also, there's no reason to believe that civilizations in the galaxy are necessarily significantly more advanced than us. Sure, other life forms could evolve more quickly than us and be more geared toward expansion in the universe, but it would take a much speedier civilization that has been borne into existence, developed advanced methods of travel and jumped the tens to tens of thousands of light years across the galaxy before we can even put a human on Mars.
There are extremely old stars in the galaxy, some nearly as old as the universe, and these stars could support much older systems, but the average age of stars in the Milky Way is just over 6 Billion years old. Our system is young in comparison, but with the wide range of different compositions, types of radiation, gravity and other factors, there's no way of knowing how long it would take life to establish itself in any given system.
Basically, the question is still up in the air. I guess we'll just have to get to work on faster-than-light travel and get our butts out there to find life!