To start with, let’s make clear that Titan is a moon that, in many ways, acts more like a planet. It has a thick atmosphere, with about 1.5 times the surface pressure of Earth’s atmosphere. None of the 177 other moons in the solar system has such an atmosphere. Plus, Titan is the only place in the solar system, other than Earth, with stable surface liquids: Titan has lakes and seas on its surface. So Titan is a remarkable, and very Earth-like, world.
Titan’s thick atmosphere is beneficial, because it means that you don’t have to wear a bulky pressure suit while you’re out and about on Titan. But the main reason I like it is simple: Titan’s atmosphere will help us stay alive. Out in space, radiation is deadly. Energetic particles from the sun, and especially galactic cosmic rays (GCRs), penetrate human tissue, causing cancer and cognitive disorders. To stay within NASA’s current cancer risk limits, astronauts can travel beyond Low Earth Orbit (LEO) for as much as 200 days; a Mars trip would likely be more like 600 days. But these damaging particles cannot make it to Titan’s surface; they’re absorbed by the atmosphere, meaning that it’s a safe environment for humans. Mars’s atmosphere is not thick enough to provide much shielding from GCRs — and Earth’s moon has little in the way of an atmosphere — so humans living in those places would probably need to live underground in order to protect themselves from radiation.