I'm certain life formed on other planets similar to how it formed here. The universe being something like 14 billion years old. Our planet is in the range of 4-5 Billion or so. There might be life several billion years old.
I dissagree that "they" could be watching us or have the means to get here easily. I believe the difficulties that we see in space travel are most likely a constant that any species would eventually face if they were advanced enough to even want to or more likely HAVE to leave their home planet.
ALL stars eventually burn out or die out. Space debris threatens impact EVERYWHERE in the universe making the threat of catastrophic collision a universal constant.
If "they" could escape they probably did it on something big with the capability to send out smaller vessels to find a suitable replacement environment to what they are biologically comfortable with.
There is no gaurantee that our atmosphere or mean temperatures would be just right for an alien's metabolism.
Here on earth there are living things right at the vents of volcanos at the bottom of the ocean.
Who knows what conditions would sustain life on other planets?
I doubt if our planet was desirable to aliens that they would hesitate getting rid of our pathetic species. All they would have to do is observe how we murder each other to come to the conclusion that we don't deserve any special consideration.
I think they watch us for the same reason we observe herds of elephants or mountain gorilla's; for study and knowledge's sake.
That is why I don't get all these alien invasion movies; there is plenty of everything else outside our planet among the debris of space. Some movie had aliens come to Earth for our water. I couldn't believe it; there is plenty of water floating through space in the form if ice debris.
Aside from that, good post, but
why do you keep putting the word 'they' in quotes?