In a nearly-real-life version of Earth there is a moderately abundant amount of alien life. However, most aliens are, in fact, not interested in humanity. So there will be no grand-landing revelation.
There are aliens among us for different reasons. Some live underground trying to escape repressive governments on their home planets, some take vacations, and others study us.
What logically and objectively speaking, with what primary justifications would an advanced alien species that has surpassed us both evolution and technology gain by studying humanity. This presumes that the aliens did not "seed" Earth with humans and that our planet isn't part of any mining/military related scenarios?