It is good to bathe.
Bathing serves several purposes:
Hygiene, and the neat physical appearance of cleanliness
Decontamination from chemical, biological, nuclear or other exposure-type hazards.
Therapy (e.g. hydrotherapy), healing, and relaxation (e.g. Blessed Rainy Day)
Religious, or, less frequently, other ceremonial rites. See Baptism
Celebration and socialization, e.g. running through fountains after winning the World Series, or jumping through a hole cut in the ice over a lake on New Year's Eve.
Ensuring people are free of certain items such as weapons or other contraband: In Chicago, Russian baths were a safe meeting place for rival gang leaders. Weapons are difficult to conceal on a nearly naked body. If the meeting resulted in reconciliation, the gangs would meet upstairs for bagels, cream cheese and borscht.  Many homeless shelters, and almost all prisons have an intake facility or intake process that includes a supervised shower with change of clothes to ensure that no contraband or contamination enters the facility.
Bathing is usually done in a bath (i.e. a place designed for bathing), but may also be done in places not specifically intended for bathing, such as rooftops (sunbathing and windbathing), a lake, river, or sprinkler connected to a garden hose.
One town known for its baths is Bath (known during ancient Roman times as Aquae Sulis), a Roman city in England famous for healing hydrothermal springs, and most recently for the Bath Spa Project consisting of a rooftop pool overlooking the city of Bath, as well as four circular clear glass steam baths. The word bath is believed to be derived from the name of the city