IMO: The only reason an Extra Terrestrial
Species has never attempted (that we know of) to acquire our extremely-polluted, trashed-up planet is because they value their health. In all probability, any intelligent species that has achieved interstellar travel no longer requires a 'home world' to exist on. Which would mean that they spend all of their lives inside whatever vessels/ships they travel in. Let's now consider how clean their environment would be compared to ours. No germs/bacteria/viruses aboard their ships to be had, and no dust. Gee, sign me up! For reasons of surviving long periods of time in space they would undoubtedly be covered by some sort of biomechanical suit (with huge sunshades covering their eyes for those times when they do venture outside their ships to explore a non-threatening world), so they would not have to avoid us for fear of contracting and dying from any of the innumerable, potentially lethal Earth pathogens. Water would be a must for their survival, of course, so it
may be necessary for them to exchange theirs on a periodic basis. However, I'm pretty sure they would avoid Earth's water because its filled with every carcinogenic chemical known to us and a higher than normal radiation level.
For all we know our music may actually scare them. But one thing is for sure: If these beings learned to travel across interstellar space in ships that defeat gravity, they would have no trouble at all exterminating we superior humans should they choose to do so. After all, reality isn't like Hollywood, and all it would take is for them to quickly create a virus or toxic agent with a 99.9% lethalality rate to Homo Sapiens Sapiens (that's us), release it into our atmosphere, and let chaos do its thing. Then, they could fly away--explore more of the multiverse--and come back in a 10,000 or so years to see if the Earth has become habitable for them. Of course, by then they would probably have discovered at least 100 other, more suitable planets to assume control of and dominion over.
Then again, who knows, maybe owning exclusive rights to The Beatles and The Rollings Stones discographies would be profitable enough for them to take hastier steps.
