Pitching an single walled tent in the rain has the advantage that the inside does not get wet. It's also quick and simple. But I try to avoid that and
if it's raining my default action is to wait for it to stop in whatever building is nearest, maybe the shower block...I don't wild camp. I've seen hammock users with large tarps that they can work under and these work well in the treed areas where they camp. But it's just another thing to carry and I don't think I'd ever use it enough to justifying bring one on tour when I can get all my gear and myself into my single walled tent in a few mins.