You are talking about empty regions.. what constitutes a region in interstellar terms? A region in earth terms may be something you could traverse by car within an hour or two so how do you apply that to interstellar distances? If FTL is possible by any means it might be that Earth-Alpha Centauri is just a short hop around the block, who knows? Maybe we live in a greater region that has a few civlizations and we just didn't encounter them or catch their radio signals because there's a ton of it flying through space on all frequencies. All i'm saying is that maybe we are not interesting enough to make official contact or we are in such a fragile state that official contact would do more harm than good so we are left alone for now. Maybe we are being studied in secret out of scientific curiosity and maybe some alien students are doing their xenobiology doctorates about us but so far no one seemed to think to contact us directly.