Three ideas for the RPG.net thread, Reasons why aliens avoid earth in a contemporary setting
Look, it's not about you, Humanity. It's those dolphins. They're just... barbarians. So crude and vulgar, you can't invite them anywhere. It's just better for the galaxy if they're shunned.
Well, they've already got Elvis and Bowie, so why come back?
This area of the Western Spiral Arm was supposed to have been cleared for redevelopment several deka-millennia ago. Somehow, Earth and its inhabitants were missed. Dreadful [procreative organ]-up, somebody's [sensory and cephalic cluster] will roll for it, I'm sure. That is, if anyone finds out about it. If there were an accident, say, and a gamma-ray clearance burster was set off without anyone making a final safety check, nobody would have to pay for evacuating the system. Just saying.