Whose to say these beings have not watched us for a long time, records have shown while the pyramids were being built in Egypt, they were building them in South America and Mexico... The huge drawings in Peru where you can only see from high above..
In the classic TNG episode, "Who Watches the Watchers", A Federation scientific outpost is discovered by a group of proto-vulcans, the vulcans watch as an away team rescues the scientist by beaming up and overhear them speaking to Picard and the vulcans refer to him as a god. Picard risks his life be being hit by an arrow to prove he was not a god but a man who has advance technology.
But as Whiskey has said,"why would the come here?" That's probably what the Indians said when scientist come to the jungles of South America to study them, who are very afraid of our technology such as cameras and cigarette lighters...
Anyway this is the other vid that is much closer and the flash is very prominet....Let's keep this discussion going...
Well, the scientists know that the Amerindians are human. The Indians probably know that the scientists are 'like them', in the sense that they're mostly similar.
But the biggest thing is that an alien civilization is just that. Alien. We have no reason to believe that they would have any remote resemblance to us, in any way. They would obviously have to have discovered most, if not all, of the technologies we have acquired at present.
But beyond that, the way that an alien would think is almost certain to be vastly different from anything a human would consider. Put it this way:
Biologically, there's stuff on Earth that looks so far removed from anything else that it might as well be alien. I'm thinking of the stuff that lives at the bottom of the oceans. So, it's likely that an alien species would biologically be just as different from us (probably more so actually) as we are from the octopi and anglerfish that live at (or near) the bottom of the ocean.
Mentally, it'd be even worse. There is simply no reason to think that an alien species will have a thought process resembling anything like a human. Certainly there would probably be some common ideas, like 'reproduce', 'survive', and 'innovate', but the complex thoughts and ideas that human civilization has formed, like the various philosophies and cultural forms of mankind, will be vastly different from something that a comparable alien civilization would have produced.
It's the case of 'aliens will think like us', which probably stems from the fact that many pop-culture scifi settings feature aliens with bumpy foreheads, leading to the supposition among many people that 'aliens will kinda look like us, so they'll kinda think like us too'.
IMO, it's rather obvious that that's not the case.