If you were lucky to hang your tarp for best weather protection (rain coming from boardside opposite good view) AND you have a large-ish tarp, it's easy to prop one (or both) side up and be able to stand up or sit in the hammock - move around. Less confined than in a tent. And many tent campers only use the rainfly. So they are out in the rain as they pack up.

But as deadeye says, that's why we have gear. Pack up under the tarp, put on rain gear, stow the tarp, and go back out on the trail.