One of the coldest camps I've ever had was a summer night in a hammock (at 10,000'). I also vowed, "Never again." I've since learned that there is a learning curve to hammock use, including using proper insulation below you. Plenty of experienced campers use and love their hammocks even in winter with proper insulation. I'd never heard of an "underquilt" when I tried out the hammock. As mentioned above, there's often a weight penalty for hammocks in those conditions, though. Hammock users typically are addicted to the comfort and consider sleeping on the ground a lower form of life.
I'm a dedicated single-wall tent user, and I see many give up on those due to condensation on their first trips. I stuck it out and learned how to deal with condensation. I was not willing to do the same with learning how to use a hammock, for instance, but I understand it's a similar learning curve. On most of my trips, finding trees is more difficult than finding an open patch of ground. I believe it's just not appropriate to tie a hammock between two large saguaros.