Here is a long answer to a short question. Sure, a lot of through-hikers "cowboy camp", in my case not so much to avoid hassle but because I love to look up into the starry sky while I'm drowsy-snug in my sleeping bag.
In fact, I don't think one avoids that much hassle by just tossing your bag and pad down to sleep. Quite often, even with clear skies, you will wake up with dew or frost on the top of your bag and you have to spend time drying it. Also, I find that a tent helps to control small items of gear that otherwise tend to wander; I loose fewer little things when I spend the night in a tent.
And finally, not as infrequently as I would have liked, I have gone to sleep with the stars shining and have awakened in the wee hours with rain falling on my face. Two AM on a high ridge with wind blowing and rain falling is not the best time to try putting up a tent: Trust me!