I think I know why I like it. For two reasons:
1. Appreciation of the size of the universe. It only took a few hours of play over a few days for me to begin have a newfound appreciation for the vastness of our galaxy. I mean I always KNEW how vast but until you play the game a bit you BEGIN to understand and appreciate this fact more. That is to say nothing about the vastness of our universe. As I continue to play and explore I find that this appreciation is expanding and deepens. I recognize the variety of everything and yet "sameness" of system (honk) after system (honk) after system....... you get the idea.
2. Seeing the human condition applied on a galactic scale. The expansion of real human history from a finite time on a finite planet..... and seeing this cast upon a whole section of the galaxy. I suppose you can get an appreciation of this from watching sci-fi and other entertainment... but flying down to a planet where you can find one solitary outpost with some poor soul's last audio file and at the same time brazillions of miles away you have some security officer representing a government that is scanning your ship at a nav beacon. Having traveled a nice cross-section of our world and appreciating time, space, and human differences that really do exist... I can recognize an echo of this same characteristic expanded far into the unknown future and spread over a section of the galaxy. Humanity has changed but is still the same.
I enjoy the variety of shipping, combat, passengers, Thargoids, ruins, exploring... but I think my mind thinking about #1 and #2 whilst I play is what is keeping me engaged.