For me, it's not a question of whether or not life exists, it is a question of time.
The time life has existed on Earth, human life especially, is so incredibly short compared to the time the universe is predicted to have existed. The conditions for life are very rare in the universe and while I am sure Earth is not the only setup to have these conditions, our window of time is so incredibly limited that our chances of (especially intelligent life) coexisting near each other are basically none.
In addition, when we are dealing with lightyears, we are not just dealing with distances. What we see happened however many years ago, and is just coming to our eye. Even if we did detect the possibility of life thousands of light years away, it's possible that those life forms have already become extinct at the point that we are observing them.