Hardin hit the nail on the head with what makes Eve so amazing.
Plot is almost completely player driven. The politicking, the scheming, the backstabbing, the big wars...the story is unfolding every day, and you're not having some pre-scripted npc tell you how it starts, develops, and ends.
What do I do to keep occupied? Patrol known pirate corridors (player pirates.) Patrol terrorist claimed space (player terrorists.) If there's a planned operation for a given day, I take part. I buy ships and position them strategically to keep me in the fight should I lose what I'm flying. I make isk by killing npcs (probably my only real npc interaction in the game.) I have tactical discussions with Clav and Ram and others.
I never have as much isk as I want or as many ships as I want, so even if there is ABSOLUTELY NOTHING going on that involves me shooting at things...I can be earning isk by killing npcs or moving stuff. I am never out of things to do because I've never "arrived" (lvl 60.)
And yes, I'll admit that there are days where Eve is little more for me than a 15 dollar-a-month chat program. Those are days where work has been a bit much and I'm not up for combat, or when I've got something to do in x amount of time and don't really have time to get involved.