If the galaxy were the size of the earth then our little solar system would be your backyard.
Look out the window into your backyard now. And I don't mean go outside and look at your back yard, because we sure as well haven't taken a good look around our own solar system yet, just look out the damn window.
Do you see any giraffes in your backyard? I doubt it. So by merely looking out of your backyard you have not seen any evidence that giraffes exist. Even though you know they do.
That's your answer. We just haven't looked thoroughly enough yet.