I've mentioned similar before elsewhere, but basically it just boils down to liking the idea of wandering and exploring the cosmos. Before getting this game I would mess around in Celestia, which is a real or virtual time astronomy 3D space sim based on star catalogs and what we know of the solar system. Other than using it for things such as identifying the moons of Jupiter seen through an optical telescope in my backyard, I'd go from star to star in it just to see the point of view from somewhere else in the galaxy, or lose myself among the stars and try to visually find my way back home to Sol and the Earth.
I liked the idea of being an astronaut when I was a little kid in the early '80s when the space race fever was still hot with the Space Shuttles, and I've also built and flown various radio controlled model aircraft and rockets as a hobby. I'm also into sci-fi.
Needless to say, when I found this game on Steam roughly two and a half years ago that simulates our entire galaxy and the stellar systems within it in a sci-fi spaceship pilot setting, it was only natural for me to go exploring in it.
What keeps me exploring in it is seeing all the various real-world nebulae and systems up close and personal as well as finding interesting arrangements of celestial bodies in procedurally generated systems. I think this is a beneficial combination of compelling game mechanics or potential, as it gives me long term goals to work toward and shorter term treasure hunts of sorts to keep things interesting while leisurely crossing vast distances in space.
I've recently finished visiting the Skull and Crossbones Nebula in my fully combat loaded Vulture,
The Ronin, completing the first leg of the current expedition I'm on, and I've previously visited dozens of real-world nebulae in it as well.
View of the Skull and Crossbones Nebula inline with Sol with the vertical axis perpendicular to the galactic plane...
16K glory shot of
The Ronin some distance out toward the rim, featuring the Milky Way Galaxy as backdrop...
An example of a rather interesting stellar system I found two years ago on my expedition to Sgr A, which I believe is now a destination of one of the passenger missions... (Spoiler: It's nearly the age of our universe, which sort of makes sense when you see the picture – I wonder what kind of life lives there and how advanced it must be to survive that environment.)