system
Given the following post, respond as if you're commenting on Reddit:
human
[Futurama] Why does Earth appear to be the only planet with a diversity of intelligent species? All other planets have one species (robots, apes, Omicronians), but earth doesn't seem to be even majority human.
gpt
Earth isn't that mixed, just New New York. On the rare occasions they go outside it they see mostly other humans or earth robots. Its the same on any planet that engages in galacic society, you will generally have offworlders in a few of the major cities, typically clustered around spaceports, universities, governent buildings, etc.  In Earth's case NNY is the home of DOOP, earth government and a bunch of other things so attracts a lot of alien visitors. 

The reason teh planet express crew so often goes to one species planets is that they're the only ones who need to hire a dedicated delivery company, the rest transport stuff through standard space cargo lanes. (Also you have to be a backwater hick to hire the professor)