Families and even communities shared bathtub water
Heating up a tub of water to take a bath was not an easy or quick operation in the past. Or even gathering enough water, to begin with. As a result, people would frequently bathe in progressively dirtier and dirtier water. Back then, people were nothing if not efficient. Because the leader of the home was seen as the most important, he would bathe first, and so on until the baby was bathed in filthy, even black, water. Some attribute the expression “don’t throw the baby out with the bathwater” to this.