Trust me, I would have felt much more secure with a tarp, I wouldn't advise it, I had a vision of me right before bed floating in a big hammock bathtub if it poured, but I was pretty confident the worst of the weather was over. This was my first hang on the trail so needless to say I was going minimalist. However, I did have an open view of the trees and stars, as well as a near full moon peaking through the quickly dissipating clouds, would have missed that with a tarp for sure. I was pretty cinched up in my sleeping bag so didn't linger on that view for too long.
It seems like we try to enclose ourselves with backpacking, we get outdoors and then shut it out, part necessity, but not always I guess. Being prepared is the best situation to be in if anything, allows flexibility.