The tradition of the Japanese bath By Trulee Lee A trait noticeably common to anime is the prevalence of the bath. However, the fascination with tubs and washing goes beyond the voyeuristic for the Japanese, and this societal trait extends to anime.
Religion plays a large part of it.
Shintoism and Buddhism, have strictures regarding ritual cleanliness. The majority of all Jpanese people bathe daily, if not multiple times daily. It has also become a social ritual, and today baths are more of a resort activity. After WWII, most people couldn't afford to have bathrooms in their house, thus the development of communal bathhouses. People didn't go to the bathhouses to get clean, they went to gossip and have fun.