Some cave debris, brought in naturally by animals or flood, is basically good. Human made trash and items aren't. Cave cleanup often consists of hauling out metal, plastic, cans, clothing, cans and glass in trash bags. Sometimes larger things, like mattresses, car bodies, old washing machines and refrigerators end up down sinkholes, and these, too, have to removed. Wood, and other biodegradable debris, especially if it has been in the cave for a long time, cause much concern.
Many animals live in and eat such things, and wholesale removal can disturb whole populations.
In such cases, much thought must go into what to do. Smoked and painted on graffiti is also a cleanup problem with its pros and cons. Prehistoric cave art or authentic signatures of famous people may have value. Signing a cave as evidence of exploration or visit was acceptable up to the the 1950's and important data can be found from examination of such things. As a rule, graffiti should only be removed after photographs are taken of anything deemed possibly significant, and after consulting with the landowner and someone knowledgeable about the history of the cave.