Cavers will use natural rigging when it is available. Many pits are bell shaped since they form from the bottom up. So they are quite easy to rig an rappel. You

Cavers will use natural rigging when it is available. Many pits are bell shaped since they form from the bottom up. So they are quite easy to rig an rappel. You tie off to some breakdown or perhaps a tree if you are on the surface and one is convenient. Your rappel rubs for maybe a few feet on the way down and then you are completely free. To get back up, you often use a system called a frog with ascenders (jumars). Trad rock climbing out of such a pit would be impossible and do far more damage. There are often formations on the walls and it climbing such an overhung situation would be impossible for most mortals who can't handle a 5.15. But sometimes bolts are unavoidable. You need to rig such that your rope won't cut itself from rubbing as you ascend. Or perhaps you need to avoid a waterfall. You set a bolt and redirect or rebelay in situations. Sometimes there is nothing to rig to as far as breakdown goes. Or you are on the surface and there are no trees or breakdown nearby. Finally, sometimes you reach a dome in a cave which is only seen from the bottom. So you need to do a dome climb up it. This typically involves setting bolts as well, though sometimes trad gear can be used. The impact of a bolt isn't very great. Cavers typically remove the hangars just leaving a hole when expedition caving. After all, they will hopefully need the hangars for something new shortly thereafter.