Here's why:

* Neptune is a gas giant: It doesn't have a solid surface like Earth, so there's no physical place to build a shelter.

* Extreme conditions: Neptune's atmosphere is incredibly hostile with extremely low temperatures (-214°C/-353°F), strong winds, and intense pressure. These conditions would make any attempt at building a shelter impossible.

* No known life: There is no evidence of life on Neptune, so there's no need for shelter for any living beings.

While we can't build shelters on Neptune, we can explore it with robotic probes! The Voyager 2 spacecraft provided us with the most detailed information about Neptune, and future missions may reveal even more about this fascinating planet.