Hypothesis 1; the aliens are going to rape the planet, enslave/eat/freeze to eat later the people. Nope. They don't need to harvest meat like we do. They can cross interstellar space, so they don't need our energy/resources. The only thing they like is our art, especially our music, and they can have that for free. They have robots to wash their dishes and stuff, those who still ingest complex carbs, that is, so they don't need human slaves which have to be fed and housed.
Hypothesis 2; The aliens are already among us, enslaving us through mind power and making us destroy ourselves so they can rape the planet, etc.
Nope. People who can travel interstellar distances aren't interested in our so-called 'resources'. They have all they want through transmutation, stellar mining, and other techniques that we haven't learned yet.
You want the truth? you think you can handle the truth? OK, here's the truth. Warning; you might not like it.
The aliens are here, making videos. To sell. For comedy. For LAUGHS!!! This is where they get their "Three Stooges" material. They already HAVE everything; the only thing they get from us is what we call the Human Comedy, what they call "The Six Billion Stooges". their audiences can't get enough. Oh, and of course our music; they like that a lot. The Beatles, Jimi Hendrix, Bach, Josquin des Près, Ali Akbar Khan, They're all superstars galaxy-wide. But mainly we're the comedy hit of the galaxy.
And THAT is the reason that they don't reveal themselves overtly; they don't want to destroy or influence the source of their best comedy sitcoms. We are the laughingstock of millions of worlds, and they don't want to lose that. They do have a prime directive; "Don't interfere when people are creating priceless comedy that can be sold all over the universe". By the way, organized religion is one of their main sources of amusement; they find the concept hysterical. You think megachurch preachers make money? nothing like the re-broadcasts on hundreds of thousands of other planets. The Tennessee snake-handlin' preacher who got bitten by a snake during a 'revival' and died (Got it? Died during a 'revival'? Yok!!!) got some of the "most high" ratings recorded. Home movies of the event (Yes, "They" had observers there recording the whole thing)... Boffo. Trillions. Classic yok. ROTFLMAO to the max, in fact some species hand to LEARN TO ROLL just so they could roll on the floor laughing whatever passes for asses among their species off. And politics? The presidential debates had people crying with laughter. The concept that we earthlings actually thought this was serious made it even funnier. Obama is the hero of the galaxy just for that one classic line. People on other planets are using "Proceed, governor…" as a ring tone.
Have a nice day, and remember to laugh at yourself. You might as well; trillions of people are laughing at your antics already. It's just too bad that you ain't getting paid for it. Go on and have a nice day!