I was really tired when I wrote this so I hope it makes sense.
It's kind of hard to explain simply.
That's the idea behind the Fermi Paradox. Besides, Earth's first radio broadcasts were only from ~100 years ago. How many aliens could hear us?
...not to mention the billions of other galaxies out there.
The universe is massive, indeed. However, it is also relatively old. Personally, I do not believe intelligent life exists elsewhere, but if I were to look at the universe from a strict hypothetical standpoint, there is simply not enough evidence to support the existence of intelligent life on other planets.
For evolutionists who believe the universe is billions upon billions of years old (maybe trillions?), the hypothesis that highly advanced alien species ought to exist because of the apparent size and age of the universe may be considered impossible because of the previously quoted "Fermi Paradox". Why?
First, for a highly advanced alien society, the size of the universe would not be as much of an issue for them as to us, in theory. New transportation methods would undoubtedly be devised that could allow an individual to go at speeds beyond our comprehension.
Second, if they had billions upon billions of years to develop they would also have billions upon billions of years to reach us. If you look at time as an almost infinite measurement, the probability that we would not have made contact with another alien species of any kind during the Earth's existence is negligible.
So the Vulcans know we're here, at least.
But, serious response. What if WE'RE the most advanced? Humans always like to entertain the notion that the aliens will come to us.
What if there are aliens, and they're simply in the stone to medieval era? Maybe we'll be the ones to find them, not the other way around.
Interesting idea for a story, but again, the Fermi Paradox. It would be extremely more probable that another alien civilization would exceed our technological levels during the existence of the universe before mankind's existence would have begun (again, hypothetically speaking; I believe the universe is relatively young compared to most theories).