You are thinking too idealistically. I'd like to say the most logical explanation is "we have nothing to offer them." Then again, what if the highest evolved life form in the galaxy is one that consumes at will. A predator that will use any and all means neccessary to gather every resource available to it. Maybe they just haven't come to our solar system yet? There are near infinite amounts of energy sources in the galaxy, so the chances of this super evolved life form hitting our sun any time soon is remote. But such a life form could exist. It's an equally valid scenario vs a civilization that is just documenting and recording ****, going on about their business quitely and peacefully.
Given these two polar opposite scenarios, you'd have to think the real answer is somewhere in between. Maybe there are intergalactic struggles going on at this very moment. I don't see why one of these idealogies can exclusively win out and dominate the galaxy, although if one has, it's unlikely we'd find out any time soon. However, I think the predator scenario becomes much less likely the longer humanity is around, because if they hear us, they would be more likely to kill us sooner than later. But it will take time scales over a few cosmological epochs before we can favor one scenario over the other.