The Rare Earth Hypothesis proposes that Earth-like planets are much rarer than we thought. The required combination of liquid water, an orbit in the ‘Goldilocks Zone’ (not too hot or not too cold), and a magnetic field strong enough to protect against radiation may be hard enough to achieve that Earth is an anomaly (Webb).
This could lend itself well to a story where humanity begins to terraform the solar system, or a story where people have to live on ships or space stations due to a lack of livable space. It would also work well for a story with an environmental message akin to ‘save the planet, it’s the only one we’ve got’.
Citations:
Webb, Stephen. “They Don’t Exist.” If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY? Seventy-Five Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life, edited by Stephen Webb, Springer International Publishing, 2015, pp. 213–329. Springer Link, doi:10.1007/978-3-319-13236-5_5.
Fermi's Paradoxical Prompts 