Ever think about how, instead of the existence of extraterrestrial beings out in space, it was actually humans? Though not written to be a heartwarming story, that is how Harry Harrison wrote To The Stars Trilogy.
Hundreds of years to the future, the dystopian world--including the space, apparently--are now only governed by one group of people. These people are only powerful because they are rich. As Earth’s natural resources depleted, humankind decided to colonize other planets. The resources, however, are hogged by the rich; the poor have to either live from the scraps or survive through the harsh conditions of the newly-inhabited planets.
We follow the story from the protagonist Jan Kulozik, an engineer, so he is one of the privileged elites that gets to live comfortably. Unfortunately, after his run-in with a group of spies which made him caught by the authorities, he is exiled to another planet. This planet is built around agriculturally. They are to produce crops to supply food for Earth and the other planets. Not long after that, the people fight back the government, but without future plans. Apparently, they were too used to living in their own colony, that they cannot stand with each other. So, in the end, to each their own, which means each colony will have their own government body.
The takeaway from this is that, while it is better for society to live within their own kind, it is important to know that when there is a threat that affects the world, humankind will always thrive together.