In general, we need to clean for the following reasons:
Maintenance and restoration: to allow the material or unit with the affected surface to be used again and perform its original intended function. Hygiene: to ensure that a surface used, for instance to prepare food, or a tool used in a hospital are safe. Adaptation and transformation: to prepare a surface for a different use, for instance to avoid cross-contamination with allergens at product change-over in the food or pharmaceutical industry. Aesthetic: sometimes we just want to clean so that our environment, some objects, or ourselves look nice!