2. They are not used to inequality.
3. No matter how strong they are, they accept the fact that humans are the most destructive species.
5.They don't enjoy politics and do not desire to be the victims of political power.
6. They get inferiority complex from Lady Gaga.
7. Male Aliens wouldn't want to risk getting their pretty female aliens being raped or abused.
8. The parent-aliens would hate their cute baby aliens to be molested by pedophiles.
9. There are aliens who loves aliens of the same sex and at no cost, they want to get assaulted and hated for what they are.
10. They cannot digest junk food.
11.They like to have the communication privacy.
12. Owing to our rigid attitude, they know it would be impossible for the humans, to adjust with foreign people and they are afraid World War III might take place.
13. They have watched every Bruce Willis and Will Smith sci-fi movies and they know how it ends.
14. They are scared they would be laughed at because they don't care about Kardashians.
15. They feel it is loathsome to keep up with the future generation of planet earth. They don't want to pull themselves a level down.
Baby Baby Baybeee ooo....Bammmm..crushed!!
17. They do not understand the concept of corruption.
18. The gas is cheaper on their planet.
19. In a nutshell, they don't want to invade a land where its citizens are evil, flawed, heartless and live with a callous attitude. It's completely not worth it.