* A new discovery: from that angle, Cassini was able to show us new rings that we'd never been able to see before.
* The wonders of modern technology: We launched Cassini on October 15, 1997. Since then it has traveled the millions of miles to Saturn (first whipping around the Sun and passing just near enough to Venus, Earth, and Jupiter to get gravity kicks to send it out to Saturn), orbited Saturn itself several times, helped us discover 2 moons of Saturn (among many other scientific achievements, including a confirmation of Einstein's general relativity just for kicks), and, of course, lined itself up nicely to place Saturn between itself and the Sun and snap that wonderful picture.
* Humility: In case you don't read the description provided by NASA, that spec of dust on the left side of the photo, just above and outside the brightest rings, is the first planet discovered by man, although it took us thousands of years from the time we first named it until the time we realized it was anything like the other planets. That spec of dust, of course, is the pale blue dot we call home.
For those who won't follow that last link, you owe it to yourself to read what Sagan said about that pale blue dot, even without a giant planet in the foreground to make it seems even smaller:
Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there - on a mote of dust suspended in a sunbeam. The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors, so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves. The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand. It has been said that astronomy is a humbling and character building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known.