Or: (4) planets are very bad places, they have diseases, nasty natives, a deep gravity well, and poisonous atmospheres as often as not. Stick to the asteroids, they're sterile, easy to get to, easy to leave, and have all the resources you really need... Sure a race or two may "feel" this way, but it ridculous to assume we don't see evidence for intelligent life, objectively, because every intelligent species likes the "asteroids".
But we DO see such evidence; look at Mars.
Read anything by Zecharia Sitchin. Look at enterprisemission.com and many others.
IF, and it's a big IF, our understanding of physics is correct, and FTL is impossible, then any visitors arriving
en masse would have most likely got here by a multi generational star ship. Scores of generations without ever setting foot on a planet. History/racial memory of planet bound life wouldn't pique desire to to actually be on a planet, indeed, the bad parts and scary monsters would end up being the prevailing view of planet bound life.
If they've been watching our TV, they may be a little reluctant to even let us know they exist...