Maybe there's something particularly fascinating about Billy Bob's bunghole that compels them to travel millions of light years to stick something up it :shrug:
In all seriousness, if there are intelligent advanced civilizations out there whom we would recognize or who would recognize us as alive and sentient they've probably got the equivalent of a big sign up above the Earth. It would read something like: "Warning! Contains primitive, violent natives who haven't learned not to foul their own nests and who will kill you if you give them half a chance. By entering High Earth Orbit you forfeit your life insurance. Remains will not be returned to your next of kin." I wouldn't trust us with advanced spacefaring technology and the ability to harness suns any more than I'd trust Hamadryas Baboons with nuclear weapons.