The reason people need to bathe mostly has to do with odor, and preventing it. The under arms (axilla) and groin (peri) areas of the body contain apocrine glands, which secrete thicker sweat than other sweat glands. This increased sweat mixes with bacteria on the skin surface, causing a strong odor, which some people find offensive.
When taking care of your parents bathing and cleansing needs, I recommend the following: Daily cleansing should include the face, peri area (groin), under the breasts, under skin folds, and the arm pits. Pericare or washing the privates may have to be done more frequently if your parent is incontinent and using diapers. Full body bathing can be done less often, as skin tends to become drier and more fragile as we age. Frequent bathing can cause dry skin, itchy skin, and irritation. When bathing an older adult, I recommend using gentle soaps which won't sting the eyes and can double as shampoo. Lotions can be helpful after bathing to prevent dry skin.